Talk:Reactive centrifugal force

Applications

I don't think the "applications" section should be here. All of the examples appear to have a closer connection to the fictitious force. Though they commonly also involve a reactive centrifugal force, it is either incidental or secondary to the mechanism being described. –Henning Makholm 03:00, 27 April 2008 (UTC)

I hope to check this later; I suspect that you are mistaken and that its removal is in fact promoting a POV. Harald88 (talk) 13:04, 28 September 2008 (UTC)

IN fact I immediately notice that it is exactly as I suspected. Thus I reintroduce that section, but keeping only the most appropriate examples. Harald88 (talk) 13:16, 28 September 2008 (UTC)

The "Applications" section has nothing to do with the reactive force that is the subject of this article. That is not a POV. It is a fundamental objection. The entire article should probably be deleted because it contains so many mistakes. But this section on "Applications" is simply misconceived and should be deleted now. The reactive (third law pair) force to a centripetal force never causes the body on which it acts to move outward. All parts of the rotating system are experiencing centripetal acceleration. All net forces are centripetal. So, if a body moves away from the centre it is due to inertia not a force. The outward movement is what is behind the "Applications" section. That is due to the pseudo "force" not the force that is the subject of this article.AMSask (talk) 20:29, 4 June 2014 (UTC)

Reply to Wolfkeeper

Wolfkeeper, there is no need to have this separate article. There is only one centrifugal force. The example that you give is exclusive on a number of counts.

(1) It concentrates on situations in which the centripetal force is supplied by an inward pressure from a contact object. David Tombe (talk) 05:59, 27 April 2008 (UTC)

Yes. That's because it applies there. In the case of the car and the rider, the car experiences the centrifugal force. In the case of a cyclist on a banked track, the track experiences the centrifugal force.- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

What about the other kinds that you have ignored?

(2) You ignore the fact that if the centripetal force were a tension from a string, then it would be the centripetal force that is the reactive force. David Tombe (talk) 05:59, 27 April 2008 (UTC)

No, I don't think it is referred to in that way.- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

You have totally ignored the tension in the string scenario.

(3) You ignore elliptical motion. David Tombe (talk) 05:59, 27 April 2008 (UTC)

Considering I was the one that put the center of curvature argument into the article, no.- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

Then why write circular motion in the disputed paragraph?

(4) You ignore forces caused by gravity, electrostatics and the Lorentz force.

Do you not see that whether consciously, or sub-consciously, you are trying to write centrifugal force and the Bucket argument out of the literature? David Tombe (talk) 05:59, 27 April 2008 (UTC)

LOL. If I'm doing something sub-consciously, then I wouldn't see it would I?- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

So basically, you are admitting that you have ignored these forces.

No, basically I'm laughing at you David.- (User) WolfKeeper (Talk) 21:16, 28 April 2008 (UTC)

Reactive centrifugal forces don't appear in every physics problem. In the case of two bodies orbiting their barycenter under gravity, electrostatic or magnetic forces I can't see that any reactive centrifugal force exists per se, and quite frankly, I don't really care.- (User) WolfKeeper (Talk) 21:16, 28 April 2008 (UTC)

I see. So you are only concerned with the tension that the centrifugal force causes in the string and the reactive centripetal force that the tension causes. In that case, you have got the terminology the wrong way around. David Tombe (talk) 08:20, 29 April 2008 (UTC)

Wolfkeeper, your example, which is actually Rracecarr's, is too exclusive. You have ignored the fact that centripetal force is the reaction force when the the motion is being caused by tension in a string. You have ignored all the points above. David Tombe (talk) 08:12, 27 April 2008 (UTC)

There are no such things as fictious and reactive centrifugal force. There is only centrifugal force. —Preceding unsigned comment added by 72.64.52.209 (talk) 14:22, 28 April 2008 (UTC)

FyzixFighter's reference to the 1996 Oxford Dictionary

FyzixFighter, What does the 1996 Oxford dictionary actually say in relation to limiting a description of centrifugal force to involve only circular motion, and pressure contact forces?

There is no evidence that your contribution here is anything other than to back up a team. It is team vanadalism. Somebody has sent for your assistance because you normally write about other topics. At the moment you are defending a very amateurish paragraph and you are simply playing out a superior numbers game. David Tombe (talk) 15:32, 28 April 2008 (UTC)

Paraphrasing, the source merely says that the general use of the term "centrifugal force" is to refer to the fictitious force that appears in non-inertial frames, but that it can also be used to describe the 3rd law pair, reactive force that is exerted on the source of a centripetal force. Where is the mention in the original version about contact forces? All I can see is a mention of Newton's third law. Nobody sent for me. I am not part of any team, and have had no previous or current dialog or contact with the other editors. I do occasionally edit physics related articles if you look far back enough in my history - in fact, I think I ran into you about a year ago on one of those pages. --FyzixFighter (talk) 16:09, 28 April 2008 (UTC)

FyzixFighter, In the example that you keep reverting, it talks about 'an object' causing the centripetal force. The only examples that I can think of under that description is a tense string or the floor of a rotating cylinder.

The example doesn't cater for gravity, electrostatics, or electromagnetism.

In the tension in the string example, the centripetal force is reacting to the centrifugal force. If there were no centrifugal force, then there would be no tension in the string. So the whole 'reactive' thing is wrong.

I have tried to re-word it more generally.

Can you please point out your exact objections to my re-wording. I had generalized it to cover all kinds of curved path motion.

If you would deal with the issues instead of just mindlessly reverting and making false accustations against me on the wikipedia administrator's notice board, then it would all end up with a more positive conclusion.

What we are aiming for is an article which is accessible to a broad range of readership.

I really do believe that the reactive centrifugal page has to go, because it is totally confusing the whole issue as well as being inherently wrong.

On a recombined page, it can then be discussed as to what centrifugal force actually is.David Tombe (talk) 08:16, 29 April 2008 (UTC)

FyzixFighter, before you revert again, can you please explain exactly what is wrong with the simple sentence that I have inserted. It describes every aspect of centrifugal force in one sentence. There is no need to involve Newton's 3rd law in the discussion.David Tombe (talk) 14:18, 29 April 2008 (UTC)

(after edit conflict) Saying 'an object' causes the centripetal force is perfectly valid and does include gravity and electromagnetic forces - when you get down to it, the contact force that you want to limit this statement to is an electrostatic repulsion. As for the term 'reactive', please see reaction (physics) to see that 'reactive' in this sense does not imply one causes the other. The two forces are simultaneous, and occur because every force has to have and equal and opposite force as described by newton's 3rd law of motion. Also, see "McGraw-Hill Dictionary of Physics" pg57 (1984 ed) which calls this the "reactive centrifugal force". Your previous rewording completely changed the meaning of the sentence - it removed the 3rd law action-reaction coupling of the two forces, and said that this centrifugal force acts on the same object that the centripetal force is acting on, which is not true. Again, here we're talking about a centrifugal force that is a reaction to the centripetal force, and therefore the two forces are not acting on the same object. They can't be if they are the action-reaction forces being described in Newton's 3rd law of motion.

As for my "false accusations", I have not wikistalked you - I have not followed you around to other articles with the intent of causing distress. You apparently have: [1] [2] [3] [4] [5]. Or is there some other reason for these edits of yours? I gladly invite any administrator to look at my edits and yours and let them judge who is wikistalking.

While we are trying to make this accessible to a broad range of readers, we are also trying to make it based on reliable sources. You have to provide one reliable source support your interpretation of physics. The other editors and I, on the other hand, have relied on modern physics textbooks and other academic sources. But I do agree with you that the two articles should be merged as the "reactive centrifugal force" is more footnote to the centrifugal pseudo-force of non-inertial reference frames. --FyzixFighter (talk) 14:25, 29 April 2008 (UTC)

FyzixFighter, You seem to be concentrating on a specific circular motion scenario in which an object is causing centripetal force by pushing on another object. That would have to be something like inside a rotating cylinder.

But in any case, it is the centripetal force that is reactive and not the centrifugal force. The cylinder floor only pushes inwards in response to the outward inertial force. It's exactly the same with gravity and normal reaction. Normal reaction of the ground is the reaction force.

Quite frankly this particular article is a mess and we are arguing to re-word something in relation to an article which we both agree should be closed down.

But it might not be closed down. And in the meantime we need to have some basic statement about what centrifugal force is. We can't confine it to circular motion. We can't confine it to contact push forces.

So can you think of a better sentence to cover the key points. The key points are (1) Curved path. (2) Outward force. And that's about the height of it.

But it should really be in the introduction to a general article on centrifugal force.

Regarding your other points, I distinctly did get the impression that you were wikistalking me. You arrived in this edit war by reverting my edits and you have been continuing to do so. You don't revert edits by other people and you needn't try and claim that they are better edits. You wouldn't dare have reverted Wolfkeeper's splitting of the article even though you disagred with it. You would have told him your views politely and given him credit for his motives and suggested to him nicely that maybe he might revert back again.

You didn't even enter the discussion until I approached you directly.

It is obvious that you are in some kind of understanding with Rracecarr.

But underlying all of this, although never explicitly spoken, is the desire of all of you to play down any information that might point to centrifugal force as being real.

Although the controversy doesn't have to enter the introduction, you don't want to have a clear exposition of the centrifugal force in the introduction. You want to emphasize in the introduction your belief that the centrifugal force is fictitious and that it is the product of observing things from a rotating frame of reference.

But you must also be aware of the fact that the centrifuge effect is real and that it is observable from all reference frames. You must know that. How could you not see that?

Yet for some reason you are very keen to play it down. Did you actually see the introduction that I wrote that triggered this edit war off?David Tombe (talk) 19:37, 29 April 2008 (UTC)

Your perception of being wikistalked does not excuse your edits (that I listed above) in an attempt to distress and disrupt other editors. Or, again I ask, what was your reasoning for making those edits?

I've only reverted edits that were in stark disagreement with reliable sources. Wolfkeeper's split, while I didn't fully agree with it, did have some basis in some reliable sources and so I had no overt reason to oppose it. Also, in cases like those, I like to give the idea some time to marinate in my mind before coming to a decision. And again, if it's so obvious that I am in some kind of understanding with Rracecarr, then why am I not aware of it.

You're still misunderstanding the use of the term reactive. Saying a force is reactive to another force does not mean that one causes the other. Also the normal ground force is not the reactive force to the force of gravity. The normal ground force is the reactive force to the object pushing on the ground. The reactive force of gravity is the force of gravity from the object on the earth. I also do not see how the current wording limits it to contact forces - Newton's 3rd law applies as much to gravity and electromagnetic forces. For planets in orbit about the sun, the reactive force to the centripetal force of gravity acting on the planets due to the sun is the force of gravity acting on the sun due to the planets. I do think that the we may need to generalize this to curved paths, but every time you add that edit in, you change far too much like removing the mention of Newton's 3rd Law and changing what the centrifugal force is acting upon (the object experiencing the centripetal force versus the object exerting the centripetal force).

We are not playing down any information that might point to centrifugal force as being real, mainly because you have not provided any. You have invoked common sense, but no reliable sources. Other editors and myself point to reliable sources, such as physics textbooks and other academic sources. Where are your reliable sources? All the behaviors that you bring up, such and cyclones, hurricanes and centrifuges can all be explained in the inertial reference frame without resorting to the invention of a centrifugal force as you describe it. --FyzixFighter (talk) 20:12, 29 April 2008 (UTC)

FyzixFighter, You keep missing the point. My edits have never contradicted the official position. I don't need reliable sources to state that a centrifugal force is the outward force that occurs when an object moves in a curved path. So you never had any basis to delete those edits.

You are making out falsely that I have been trying to put controversial material into the main article.

You also miss the point about cyclones and centrifuges etc. I know that all those effects can be explained by inertia.

All I was saying was that they are real effects. They can be viewed from space. None of those effects needs to be viewed from a rotating frame of reference but the articles are pushing the line that these effects can only be viewed from rotating reference frames.

It is clearly not true. They are real effects. Call it inertia or centrifugal force, but they are real effects. When large particles push through smaller particles, that is a real effect viewable from any frame of reference.

Your side are trying to avoid a simple description of centrifugal force and to cloud up the introduction with statements such as that centrifugal force is something that can only be observed from a rotating frame of reference. And that is clearly untrue.

And you are twisting all that about the object causing the centripetal force. The centripetal force is the reaction force. There is no doubt about that. The centrifugal force is the outward acting force.

And you further twisted the bit about the object. The article clearly mentions an object, so clearly it is not talking about gravity or electromagnetism. I suppose you might want to argue that pressure comes from electrostatic repulsion at microscopic level. But the truth is you have been deleting good edits and replacing them with bad edits for no other reason than to support a team.David Tombe (talk) 20:32, 29 April 2008 (UTC)

I never said the effects weren't real, just that the cause of the effects do not require the inclusion a centrifugal force. When writing out the sum of the forces to do F_net=ma (which is only valid in inertial frames) to get the equations of motion, there is no centrifugal force term there. Inertia is not a force as defined by any reliable sources or in any of the academic literature.

Further, to provide a quote of the material a paraphrased above from Oxford's "Dictionary of Physics":

Occasionally the concept of a centrifugal force can be useful, as long as it is recognized as a fictitious force. A true centrifugal force is exerted, as a reaction, by the rotating object on whatever is providing its centripetal force.

I cross-references the term "reaction" to a definition similar to the one found at reaction (physics). --FyzixFighter (talk) 23:24, 29 April 2008 (UTC)

FyzixFighter, what name would you like to use for the effect that occurs in a centrifuge? And is it a real effect? David Tombe (talk) 12:53, 30 April 2008 (UTC)

It's irrelevant what name I would like to use. What effect does the academic literature call it? From the sources I've looked at, they refer to the process as sedimentation. That effect is real - no argument there. Our disagreement is what causes the effect. A centrifugal force only appears when one naively tries to apply Newton's second law to a rotating frame (it's only valid in inertial frames, see Hand & Finch "Analytical Mechanics, pg 267). When the physics is done in the inertial frame where Newton's 2nd is valid, no centrifugal force term appears in the sum of forces, and therefore one can get the same effect without introducing a centrifugal force. At least, that's what I've seen in all the reliable sources I've checked.

Again, inclusion isn't determined by whether or not the physics makes sense to every editor; it's determined by reliable sources. Do you have a reliable source that says the effect is caused by a real, non-pseudo centrifugal force? --FyzixFighter (talk) 13:14, 30 April 2008 (UTC)

FyzixFighter, I see. You are denying that the centrifuge involves centrifugal force. You are totally out of line with the general understanding of the term centrifugal force. You are trying to introduce some mathematical meaning for the term that has totally lost touch with the original meaning.

In that case, in what topic would we deal with things such as the centrifuge, Newton's bucket, and people getting flung to the side door of a swerving car? David Tombe (talk) 13:33, 30 April 2008 (UTC)

David: what you are calling 'real centrifugal force' I would call 'inertia.' The object which seems to be experiencing an outward force is only reacting against a centripetal force acting inwards. Granted that's a subtle point, but every textbook on classical mechanics I've read expresses it in a similar fashion. I've got to side with FyzixFighter on this. I'm not surprised by your disagreement, because the physicist's definition of 'centrifugal force' is not the same as the lay definition, therefore the confusion. A better explanation in the article would be a good thing, but it's hard to do because the difference is subtle. (And before you raise the argument, inertia can kill you, too.) Plvekamp (talk) 14:22, 30 April 2008 (UTC)

I'm not denying that the centrifuge involves centrifugal force, every reliable source I can find is denying it. To quote one of them, the centrifugal force, Coriolis force, and Euler force "aren't real forces; they are purely kinematic consequences of the rotation of the body coordinates." When the physics is done right, applying Newton's 2nd law in the inertial frame where it is valid, none of those three forces show up in the sum of the forces, and yet the observed effects are predicted. Again, when the physics is done right, the behavior seen in the centrifuge can be explained without involving a centrifugal force.

All those situations you mention deal with a rotating frame, and therefore the centrifugal (pseudo)force and should be handled there. This article is to deal with the true centrifugal force that the moving object exerts on the source of the centripetal force, forming an action-reaction pair as predicted by Newton's 3rd law. Of course, this only occurs in some instances, since when considering gravity and orbital motion both forces in the action-reaction pair are centripetal.

Again, where is your reliable source that the centrifugal force in those situations is a real force and not a pseudoforce? --FyzixFighter (talk) 14:52, 30 April 2008 (UTC)

Plvekamp, I would agree with you that inertia is effectively the same thing as the parent effect of both centrifugal force and Coriolis force. But let's keep this discussion to centrifugal force. Supposing inertia and centrifugal force are the same thing, and supposing it is an absolute real effect as can be seen by the diffusion effect in the centrifuge. Then we are merely splitting hairs if we try to limit the application of the term centrifugal force to the situation as when we view it from the rotating reference frame. It is silly to say that it is centrifugal force as far as a man riding in the centrifuge is concerned, but that the man sitting in the corner of the room is not allowed to use that same name.

There are other complications which I am trying to sort out as well. This business of reactive centrifugal force doesn't need to enter into the discussion. When the heavy particles in a centrifuge are accelerating out to the edge, they are experiencing centrifugal force. When they reach the edge, a centripetal force constrains them to circular motion in conjunction with the centrifugal force. We have an action-reaction pair. But this is an extension of the core issue and doesn't need to be discussed in the introduction.

Anyway, that explains why I wanted to drop rotating reference frames from the description altogether. They are superfluous to requirements as far as decsribing the actual effect is concerned.

But there are some editors here who are very much focused on the mathematical equations for transformation to a rotating frame of reference and they are very adamant that the term centrifugal force should only ever be applied inside the rotating reference frame.

The next question surrounds the issue of whether centrifugal force is real or fictitious. Well simply saying that it expresses the effects of inertia in the rotating frame doesn't make it fictitious.

But the problem gets more complicated. We then enter into the Bucket argument which in my opinion is a variation of the Faraday paradox. Is the radially outward effect that causes hydrostatic pressure in the bucket of water the same situation as when we view a stationary bucket of water from a rotating frame of reference?

I say that it is not the same. The latter effect is totally fictitious.

But by using the maths for rotating reference frames, there is a school of thought which believes that these two effects can come under the one mathematical umbrella and that hence we can formally declare centrifugal force to be fictitious always.

This is a gross error in my opinion. The stationary bucket is not the same as the moving bucket with the centrifugal hydrostatic pressure. One is a fictitious effect and one is a real effect.

So how do we word the introduction? Well we have to find a compromise between the modern precise mathematical terminology and the understanding of the term by the man in the street. We have to concentrate on the real effect. David Tombe (talk) 17:19, 30 April 2008 (UTC)

FyzixFighter, I think that you are missing out on the subtelty of the Bucket argument. Even if we restrict the term centrifugal force to rotating reference frames, forgetting about this so-called reactive centrifugal force, there will still be two kinds of situation to contemplate. It's the Faraday paradox. Is the situation of co-rotation in which an outward radial pressure occurs, the same as the situation when the object sits stationary and we view the artificial circle from the rotating frame.

You may argue that both situations are united under the same umbrella maths. But you could say that about the Lorentz force too in relation to the Faraday paradox. I personally believe that the maths in question is only correct, and was only derived to cater for co-rotation, and that its application to the stationary object is heavily flawed. But that doesn't matter. Put the maths aside, and it is still obvious that the physics of the two situations is different.

You need to appreciate that there are two distinct physical situations to contemplate. And only one of them is centrifugal force. Call it inertia if you like, but only one of those situations is inertia/centrifugal force.

So you can't introduce centrifugal force under the allegation that it is fictitious. What you do is, you describe it in the introduction and discuss the controversies in the article. David Tombe (talk) 17:31, 30 April 2008 (UTC)

Sorry, no. I'm basing my arguments not on my personal understanding of physics, but on reliable sources. You're trying to introduce original research ("I personally believe..."). Where is the reliable source that says the centrifugal force is not a pseudo/fictitious force but a real force as you describe? Until you provide one, the introduction will introduce the centrifugal force as it is described in the reliable sources, as a kinematic consequence of a rotating frame and not a real force. --FyzixFighter (talk) 17:41, 30 April 2008 (UTC)

FyzixFighter, so many sources describe it in different ways, and collectively they illustrate that there is great confusion over the term.

We don't need a source to confirm that the effect that takes place in a centrifuge is real. We can see it so clearly without needing a written source to confirm it.

Can you actually appreciate that there are two distinct effects as per the Bucket argument. One is an outward radial pressure that is real, and the other is an artifact circlular motion as in the diurnal rotation of the celestail sphere?David Tombe (talk) 18:28, 30 April 2008 (UTC)

No, the sources do not describe it in different ways. All reliable sources describe this as a pseudoforce, ie not a real force. I'm not asking for a source for the fact that the effect in a centrifuge is real. I'm asking for a source that the effect is caused by a real centrifugal force and not a pseudo centrifugal force. This is really quite simple, all you have to do is provide a reliable source that the centrifugal force is a real force. Until you do, the changes you want to add violate WP:OR,WP:RS, and WP:FRINGE. --FyzixFighter (talk) 18:36, 30 April 2008 (UTC)

FyzixFighter, now you are just being silly. If the centrifuge effect is real, then the centrifugal force is real. No textbook citations are necessary to prove this fundamental fact.David Tombe (talk) 18:41, 30 April 2008 (UTC)

Whether or not that is so, within the wikipedia, unreferenced material can be removed at any time.- (User) WolfKeeper (Talk) 19:53, 30 April 2008 (UTC)

Wolfkeeper, under wikipedia rules, obvious facts don't have to be referenced. And anyway, there were no unreferenced facts in my latest writing of the introduction. You reverted as a knee jerk reaction, on the assumption that I had written a clause stating that centrifugal force only occurs during co-rotation. When you realized that you had read it wrongly, you dug in nevertheless, and to save face you are now trying to deny hydrostatic pressure in a rotating bucket.

You have demonstrated that you are not in a position to be editing articles about real physics. David Tombe (talk) 09:44, 1 May 2008 (UTC)

Misleading inaccuracy had slipped in - compare with old version

Compared to the old full article http://en.wikipedia.org/w/index.php?title=Centrifugal_force_(rotating_reference_frame)&oldid=196032047 regretfully at least one misleading inaccury had slipped in, together with the removal of a reference that avoided that inaccuracy. I now corrected that and will put the reference back. There may well be other new errors or erroneous suggestions. -> please compare the two versions to check this article. Harald88 (talk) 13:02, 28 September 2008 (UTC)

If you use polar coordinates in an inertial frame a term appears that is called 'centrifugal force/acceleration' and another called 'coriolis force/acceleration'. Are these not fictitious forces?- (User) Wolfkeeper (Talk) 14:13, 28 September 2008 (UTC)

They are, but not according to the point of view that centrifugal force must vanish in an inertial frame. Calling the polar coordinate term rω² a centrifugal force, where ω is not the rotational rate of the frame, but that of the particle seen from a stationary frame, is a horrible misuse of terminology that flies in the face of the whole history of classical mechanics from the rotating bucket experiment all the way to the present definition of inertial frame. (Take a look at inertial frame). It also has no meaning whatsoever in ordinary experience: if you stand or walk on a stationary carousel this rω² "fictitious force" has absolutely no effect. If you stand or walk on a rotating carousel the usual fictitious force rΩ² (where Ω is the rotational rate of the carousel) acts upon you, and the rω² mathematical centrifugal force still has no effect upon you. If you want to predict weather patterns, the rω² centrifugal force has no role, only rΩ². (Actually the Coriolis term is more important, but the same argument has a parallel for Coriolis force.) Apparently I haven't got across the "two terminologies" idea, eh? Brews ohare (talk) 19:26, 28 September 2008 (UTC)

I think your view has merit, but the reliable sources use it in the way that I indicate. Fictitious forces are not only about rotating reference frames. I agree that they are not the same fictitious forces as in the rotating reference frame.- (User) Wolfkeeper (Talk) 21:13, 28 September 2008 (UTC)

Do you mean all "the reliable sources" or "some reliable sources"? Here's a question: suppose you walk around a stationary carousel in a circle at at angular rate ω.

1. Then the "inertial frame" guy will say you are subject to a centripetal inward force exerted, lets say by your sneakers upon you. There are no other forces.
2. The polar coordinate guy says your acceleration (as he calls it) is only d²r / dt² = 0 because your radius is not changing. He explains that by saying that there is (what I will call) "phony" centrifugal force ω² r, which of course, balanced the centripetal inward force resulting in zero "acceleration" d²r / dt².

Now what do the two guys say to the poor student of classical mechanics who is told that Newton's laws are the same in all inertial frames (Special principle of relativity)?

1. To the inertial guy there is really only a centripetal force supporting a circular motion. That's true regardless of your choice of coordinates: describe the path in Cartesian, polar, elliptic or whatever.
2. To the coordinate guy, yeah it's an inertial frame. But just a minute: in Cartesian coordinates there is only a centripetal force. But in a polar coordinate system, there is zero net force, even though the guy is in a circular path. And in elliptical coordinates or some cockamamie set of q_k coordinates? According to the coordinate guy there is some outward force opposing (but not necessarily balancing) the centripetal force, but to make d²q_k / dt² = 0 , who knows what the fictitious force is? Stay tuned while I get out my differential calculus. Or better yet, tell the guy to stop walking in a circle and go in a path where d²q_k / dt² = 0; that'd make my calculations easier.
3. To the guy doing the circular walk, in a non-inertial frame where he is stationary, its pretty clear: he has to fight that centrifugal force rω² or he's going off in a straight line: don't tell me about some "phony" d²q_k / dt² = 0 .
4. To Fugal: the inertial guy is nuts: he always uses Cartesian coordinates, even if he thinks he isn't. He should get a book and read up. And by the way, watch out: these authors can be tricky. Brews ohare (talk) 22:07, 28 September 2008 (UTC)

BTW, this discussion probably is irrelevant to Reactive centrifugal force because it is a reaction to centripetal force, and there ain't no doubt about that. Brews ohare (talk) 23:47, 28 September 2008 (UTC)

There is no such thing as reactive centrifugal force

There is no such thing as reactive centrifugal force. When an object is swung in a circle on the end of a string, the tension in the string causes an inward acting centripetal force to act. The reaction to the centripetal force is the equal and opposite centripetal force acting on the pivot.

It seems that by being equal and opposite to the centripetal force, the reaction cannot be centripetal, that is towards the center. But that is all beside the point. The simple fact that there is a reference, published by Princeton University Press, no less, means that at least one reliable source says that there is such a thing, and that's what is important on Wikipedia. If another, similarly reliable, published source could be found that asserts that there is no such thing as reactive centrifugal force, then we could update this article to state that "some authors say that it does not exist." -AndrewDressel (talk) 01:45, 12 April 2009 (UTC)

The tension in the string is initially caused by the outward centrifugal force. This outward centrifugal force is the same centrifugal force that appears in the radial planetary orbital equation, and which is treated in another article but without its name being mentioned. See the planetary orbital section in centrifugal force (rotating reference frame).

It is the same centrifugal force which arises in rotating frames of reference when the object in question is co-rotating with the frame.

There is only one universal centrifugal force. David Tombe (talk) 00:08, 12 April 2009 (UTC)

Andrew, what exactly does your one reliable source say? What are the exact words?

Well, it was tricky, but I clicked on the link provided, and Google Books was kind enough to highlight the relevant text in yellow. This is what it says on page 47: "Similarly, the sun will feel such a reactive, centrifugal force from each of the planets that it holds in a orbit by its force of gravity." The third reference given, Fluid Mechanics, published by PHI Learning Pvt. Ltd. in 2004, also appears to be reliable. Again, Google Books reveals the exact quotation on page 121 to be "Note that the reactive centrifugal force on the CV acts outward." -AndrewDressel (talk) 15:03, 12 April 2009 (UTC)

If it's just a case of needing one single reliable source, then that is a recipe for disaster, since there are so many conflicting sources. This problem needs to be analyzed rationally over a balance of sources and natural reasoning.

It turns out that there is more than one. Are there any that assert that "there is no such thing as reactive centrifugal force?" -AndrewDressel (talk) 15:03, 12 April 2009 (UTC)

On the point which you made above, the reacting centripetal force on the pivot will also be towards the centre from its own perspective.

If the pivot were also moving about the center 180 degrees out of phase with the object, sure, but what if it were stationary and actually at the center? At every point along the string, each segment will experience a centripetal force from the next inboard segment, and a centrifugal force from the next outboard segment. -AndrewDressel (talk) 15:03, 12 April 2009 (UTC)

Andrew, both of the two centripetal forces will act inwards towards the common centre of mass in every situation. And both of the two centrifugal forces will act outwards. We will have two sets of action-reaction pairs. In a circular motion, all four forces will be equal. But in elliptical motion, the centrifugal force and the centripetal force will not be equal in general. The centrifugal force and the centripetal force do not form an action-reaction pair, even in circular cases where they are equal in magnitude. David Tombe (talk) 21:20, 12 April 2009 (UTC)

The centrifugal force which appears in the planetary orbital equation is the one and only centrifugal force. Imagine that we could switch gravity off and then attach a string from the Earth to the Moon. The centrifugal force in the Kepler problem would still exist, and it is the force that would pull the string taut. Once the string had been pulled taut, the tension in the string would then serve to act as the centripetal force which would keep the Moon in orbit.

So as you can see, the centrifugal force is neither fictitious, nor reactive. This topic can be easily handled inside one single article. The only reason why it was split in the first place was to hide all evidence that centrifugal force might not be entirely fictitious. The misunderstood notion of reactive centrifugal force tread too dangerously on the idea that centrifugal force might be real, and so it was removed to a separate article which doesn't get first hits on google searches.David Tombe (talk) 12:44, 12 April 2009 (UTC)

No, it was split because the reactive centrifugal force acts on an entirely different object to the centrifugal force.- (User) Wolfkeeper (Talk) 14:42, 12 April 2009 (UTC)

For example in a ball bearing, reactive centrifugal force acts on the outer races, but centrifugal force acts on the balls, (and even then it only acts on the balls when viewed from a rotating reference frame.- (User) Wolfkeeper (Talk) 14:45, 12 April 2009 (UTC)

I support Wolfkeeper on this one. If time is taken to understand the comparative table at Reactive_centrifugal_force#Fictitious_forces, any confusion should be resolved. Brews ohare (talk) 17:03, 12 April 2009 (UTC)

It's the same analogy as between weight and gravity. Gravity acts on an object. That object's weight then pushes on the ground.

The concept which is being described in this article is the effect which an object that is being acted on by centrifugal force, transmits to another object. Basically the concept which is being described here is to centrifugal force, what weight is to gravity. That is not a basis for having two separate articles about centrifugal force. That could all be described in a single centrifugal force article, because the centrifugal force which causes the knock on effect is the very same centrifugal force that you are describing for co-rotating objects in rotating frames in the other article. And that centrifugal force is the same centrifugal force that appears in the planetary orbit equation.

And the knock on effect which you are describing here is not even reactive. It is the pro-active mechanism which pulls a string taut, or which pushes on the floor of a rotating cylinder so as to induce the tension in the string or the normal reaction. It is the centripetal force that is reacting in these situations. Not only are you wrong to split the article, but you have also got cause and effect the wrong way around. David Tombe (talk) 21:15, 12 April 2009 (UTC)

This viewpoint that everything should be done in one article is a mistake. Both articles are necessary. Read the comparative table at Reactive_centrifugal_force#Fictitious_forces. Brews ohare (talk) 04:20, 13 April 2009 (UTC)

Andrew and Brews, Yes there are indeed references which use the term 'reactive centrifugal force'. But these refer to the one and only centrifugal force.

Consider this all inclusive example. Two objects move with mutual transverse speed. There will be a gravitational force and a centrifugal force as per the planetary orbital equation. If the gravitational force is very weak, then the orbit will be a hyperbola.

Now attach a string between the two objects. The centrifugal force acting on the two objects will then pull on the string. It is this latter effect which is covered by this article. The pulling effect on the string will make the string go taut and introduce a tension. This tension will give rise to an inward centripetal force which is greater than the gravity, and the orbit will become circular.

That is the entire topic of centrifugal force in a nutshell. We cannot have two articles just to cater for (1) the centrifugal force on the objects, and (2) The centrifugal force which the objects then transmit to the string. David Tombe (talk) 11:59, 13 April 2009 (UTC)

There is no such thing as reactive centrifugal force (again)

This sentence in the first paragraph: "This reactive force is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration." is not generally true. It is certainly not true in the case of two bodies in gravitational orbit about each other. In that case there are only two forces: the gravitational forces of each body on the other. Both forces are centripetal. Each body exerts a force on the other causing the other to accelerate centripetally, ie. toward the centre of rotation, which is the centre of mass of the two body system.

The reference is to Delo E. Mook & Thomas Vargish (1987). Inside relativity. Princeton NJ: Princeton University Press. p. p. 47. Unfortunately, this reference is wrong in attributing the force of the earth on the sun as being a centrifugal force. The force of gravity of the earth on the sun, causes the sun to accelerate toward the centre of rotation, which is the centre of mass of the earth/sun system, so it is centripetal. -AMSask (talk) 19:04, 15 September 2011 (UTC)

I agree that gravitational attraction seems to be a situation in which the reactive centrifugal force as described in this article isn't really centrifugal. As the moon orbits the earth, it does pull on the earth, but towards their common Barycenter, not away from it. Yes, the reference seems to provide a poor example. Perhaps we should narrow the definition, if we can find a better reference.

I believe it is incorrect, however, to describe the gravitational attraction between two bodies as two forces. Instead, the bodies are pulled towards each other by opposite ends of the same force, as described by Newton's third law. -AndrewDressel (talk) 19:25, 15 September 2011 (UTC)

??Opposite ends of the same force? You can have opposite ends of a rope with tension. But gravitational force does not have "ends". The bodies simply exert equal and opposite attractive forces on each other at a distance. That is what Newton's Law of Universal Gravitation says. Both bodies experience acceleration so both bodies have forces acting on them, the force on one being equal and opposite to the force on the other. AMSask (talk) 04:00, 17 September 2011 (UTC)

I don't see where Newton's Third Law is limited to ropes or any other type of force; it applies to all forces. Hellingman explains that all forces are interactions between different bodies, and there is no such thing as a unidirectional force or a force that acts on only one body.(C Hellingman (1992). "Newton’s third law revisited". Phys. Educ. 27 (2): 112–115.) Thus, the ends of a gravitational force are the two masses that attract each other. -AndrewDressel (talk) 13:26, 17 September 2011 (UTC)

It is undeniable that forces come in pairs. So I am confused by what you meant then by: "I believe it is incorrect, however, to describe the gravitational attraction between two bodies as two forces." In the sun-earth system, there is the force of the sun on the earth and the force of the earth on the sun. Those are two forces because they operate on two distinct bodies and cause two distinct accelerations. I have not heard this terminology before about the "ends" of a force. AMSask (talk) 15:24, 18 September 2011 (UTC)

It is completely deniable that forces come in pairs. Even Newton did it, as Hellingman points out:

"In the end of the third book of the Principia we find the following passage, wherein Newton explains why the forces celestial bodies exert on each other are proportional to the masses of both bodies. In Cajori’s (1966) translation:"

"For all action is mutual, and makes the bodies approach one to the other, and therefore must be the same in both bodies. It is true that we may consider one body as attracting, another as attracted; but this distinction is more mathematical than natural. . . . It is not one action by which the Sun attracts Jupiter, and another by which Jupiter attracts the Sun; but it is one action by which the Sun and Jupiter mutually endeavour to come nearer together (by the third Law of Motion); and by the action with which Jupiter attracts the Sun. Likewise Jupiter and the Sun endeavour to come nearer together. But the Sun is not attracted towards Jupiter by a twofold action, nor Jupiter by a twofold action towards the Sun; but it is one single intermediate action, by which both approach nearer together." (emphasis mine)

"One single intermediate action! One can almost hear the word interaction, much in use nowadays." (emphasis Hellingman's)

Hellingman continues by explaining why this seemingly trivial distinction is important:

"Interpreting forces as sides of a single interaction implies a very important shift of focus of attention. The attention is drawn away from the objects themselves to ‘somewhere’ between the objects. Failure to see the ‘between’-like character of a force lies at the bottom of all misconceptions."

-AndrewDressel (talk) 06:44, 19 September 2011

There are many different ways of mentally picturing or modeling the concept of force. But one cannot deny that in a two body interaction there are two distinct bodies (masses) and each have distinct rates of change of momentum. So, unless you redefine force as something other than dp/dt, there are two forces. AMSask (talk) 21:33, 18 September 2011 (UTC)

I am not sure what you mean by "distinct". If you mean "different", then by saying "each have distinct rates of change of momentum", it sounds as if you are saying that dp/dt of one mass does not equal dp/dt of the second mass. If force is defined as dp/dt, then it seems that you would be saying that the force that acts on one mass is not equal in magnitude to the force that acts on the second mass, and that would contract Newton's Third Law, independent of whether we consider the force between two objects as a single force or two separate forces. Instead, if by "distinct" you mean perhaps "equal but separate", then I cannot understand how you conclude that there must be two forces. I see no reason why a single force cannot change the momentum of two different particles equally, just as the tension in a single rope or spring would if either where attached to both of the particles. -AndrewDressel (talk) 01:56, 19 September 2011 (UTC)

The magnitudes of the two forces are equal. But they operate on two different bodies and in two different directions. So the forces can be readily distinguished. The reason there are two different forces is because force is defined as the time rate of change of a body's momentum vector as measured in an inertial frame of reference. If you want to use a different definition of force, you will have to be clear how you define it and you should probably call it something else. AMSask (talk) 04:13, 19 September 2011 (UTC)

I think now I see your point. Newton took care to explain that gravitational attraction "is one action by which the Sun and Jupiter mutually endeavour to come nearer together", but perhaps for the sake of calculation, the preferred current convention is to think of a single force as the change in momentum of only one distinguishable mass at a time. Perhaps I must retract my assertion that "it is incorrect to describe the gravitational attraction between two bodies as two forces" and leave you to wrestle with Dicklyon about what to call them. -AndrewDressel (talk) 12:56, 19 September 2011 (UTC)

It is not a "preferred current convention" to think of a single force as the change in momentum of only one distinguishable mass at a time. It is the very essence of the meaning of "force". Similarly, we don't say it is a "preferred current convention" to speak of a body's acceleration as the rate of change of its velocity. AMSask (talk) 16:22, 19 September 2011 (UTC)

I think I may have spoken too soon. If force is strictly defined as dp/dt, then what of forces that do not cause a change in momentum of an object? Must they be zero or not be forces? My mechanics textbook even begins with "force can be defined by the amount of spring stretch it causes." At the same time, if force is defined as dp/dt, are we to assume that it has only one end and changes the momentum of only one object at a time? No, I don't see where it is written that the very essence of the meaning of "force" is the change in momentum of only one distinguishable mass at a time. Instead, it is often written that force can be defined as dp/dt, but by Newton's third law, we know that it must change the momentum of two objects at the same time, unless additional forces are applied simultaneously to the second object. -AndrewDressel (talk) 17:13, 19 September 2011 (UTC)

You can say that the interaction of two bodies causes the momentum of the two bodies to change at the same time. You can say that the interaction causes each body to exert a force on the other body that is equal and opposite to the force that is exerted on it by the other. Those forces cause the changes in momentum that result from the interaction. But if you are saying that it is a (single) force that changes the momentum of the two bodies at the same time, this would not be correct.AMSask (talk) 03:17, 20 September 2011 (UTC)

Where is this written? I cannot find it in the Principia, my mechanics textbook, or a peer-reviewed journal. Where have you found it? -AndrewDressel (talk) 13:02, 20 September 2011 (UTC)

You will have to read your textbooks more carefully. Here is an example of the kind of problem discussed in virtually every introductory textbook on physics: Consider a 10 kg block moving at 1 m/sec colliding simultaneously with a 1 kg block and a 2 kg block on a frictionless surface. The collision lasts .01 second. Calculate the (average) forces that arise in this collision. The answer is not: "There is only one force". If you disagree, I would be very interested in your answer for the value and direction of that force. There are three objects and each object experiences a different change in momentum. At any given moment there is a different force on each of the three blocks.

You should be careful about how you use the "it is not found in any physics text" argument. You will not find any discussion of "reactive centrifugal force" in a physics textbook because no one uses the term. It is at best a poor and misleading term, and in the example given by Mook and Vargish in their book it is quite wrong, for the reasons I have given.AMSask (talk) 19:11, 20 September 2011 (UTC)

In the case of the reactive force of the Earth on the Sun, the direction of the force is toward the Earth. From the point of view of the Sun relative to the center of the system, this is centripetal (or nearly so, so non-circular orbit), but that's not what reactive centrifugal force is referring to. It's the force that an object in circular motion exerts back on the object providing its centripetal force; it's in the opposite direction of the centripetal force; from the point of view of this object moving in a circle, it's centrifugal, away from the center of its osculating circle. Yes, it may be an awkward deprecated concept, but it's not nearly as bad as what you'll have if you start calling it sometimes centripetal. Dicklyon (talk) 16:00, 17 September 2011 (UTC)

There are two distinct forces in a two body gravitational interaction. Both arise from a single gravitational interaction. There is the force on the sun by the earth that results in a centripetal acceleration of the sun toward the earth-sun centre of mass. And there is the force on the earth by the sun, which also results in a centripetal acceleration of the earth toward the same point. If we define force = dp/dt then there are two forces. If you define force as the interaction, then you end up with a completely different definition of force. Before you can talk about the "force" as being the interaction you have to define what you mean: how does it relate to dp/dt?

In a two-body interaction, each force can be considered an action force or a reaction force. Action and reaction are poor terms to use because it suggests that the "reaction" force arises after or in response to the "action" force - ie. that they are not simultaneous. The conservation of momentum, which appears to be an inviolable principle in all physics, depends on both forces applying simultaneously.AMSask (talk) 21:33, 18 September 2011 (UTC)

If you want to fix the sentence in question, change it to "This reactive force is directed away from the center of rotation of the rotating mass, and is exerted by the rotating mass on the object that originates the centripetal acceleration." Or, since "away from the center" is not a direction at all, you can put "This reactive force is directed from the center of rotation of the rotating mass toward the rotating mass, and is exerted by the rotating mass on the object that originates the centripetal acceleration." Dicklyon (talk) 16:00, 17 September 2011 (UTC)

But that would be completely wrong. In a two body interaction involving rotation there are only two forces. Each body exerts a force on the other. There are only two bodies that accelerate: both accelerate toward the centre of rotation. If you draw the second time derivative of the radial displacement vector of the centre of mass of each body, the direction of that vector will be opposite to the direction of the radial displacement vector of that body. If you multiply that acceleration vector by the body's mass, that is the definition of a centripetal force. There is no acceleration that is in the same direction as the radial displacement vector of the accelerating body. AMSask (talk) 21:33, 18 September 2011 (UTC)

I have reviewed the Mook book, and I don't see anything wrong there; it does not claim that the directions of the reactive centrifugal forces on the Sun are anything but toward the planets. And with all those planets jerking the Sun around, the motion is not anything like circular about a center anyway, so you certainly can't be right to suggest that the force is centripetal. Dicklyon (talk) 16:00, 17 September 2011 (UTC)

First of all, the direction of a (net) force on a body is the direction of the acceleration of that body. ${\vec {F}}={\frac {d{\vec {p}}}{dt}}=m{\vec {a}}$. Whether the orbit is elliptical, circular, parabolic or hyperbolic, the acceleration, hence force, is always centripetal (opposite to the body's radial displacement from the centre of rotation). The sun only accelerates toward the earth in the non-inertial frame of reference of the earth. In an inertial frame of reference, both the sun and the earth accelerate toward the centre of mass of the sun-earth system (assuming there are no other planets).AMSask (talk) 21:33, 18 September 2011 (UTC)

Here's another book (old) about the concept; not very clear about what the force is exerted on, but clear about the direction being opposite to the centripetal. Here is a newer book. and here is a 1905 Science mag discussion this concept in books, and they think it's a bad idea that should be retired (a discussion still going on today, though it has mostly been done). One of the books they're reviewing is here; it's clear what direction is meant by centrifugal, as it's with respect to the body's center of curvature of motion, nothing to do with the body that the force is acting on. Dicklyon (talk) 16:00, 17 September 2011 (UTC)

Dragging up books from 1905 is not the way to write a WP article. Of course, you can call any force acting away from any instantaneous centre of rotation a centrifugal force but this serves no useful purpose and is very confusing to many people. This usage has been completely dropped by modern engineers, physicists, and mathematicians and has no place here except in a historical context. Martin Hogbin (talk) 09:55, 13 March 2012 (UTC)

The recent edits

Wolfkeeper, your tidying up of that last line in the introduction was actually OK. It is in line with my own edit on the issue. But there wasn't really any need for the re-wording, although I know that you were undoing what Dick undid.

Nevertheless, there was no need to then erase my history article. Dick erased it first and it was in effect an act of spiteful vandalism. The contents of that edit were straight out of the supplied source, and the notorious dispute between Leibniz and Newton and its relation to the history of centrifugal force is very relevant for this article, especially since you are the one that insists that the Newtonian interpration be given a special page of its own. David Tombe (talk) 12:56, 3 May 2009 (UTC)

Oh, come on, David -- spiteful vandalism? If you had even one other editor backing your idiosyncratic point of view we might have something to discuss, but for you to try to use Newton and Leibniz as a vehicle to push your strange understanding of physics is just not something we're likely to allow here. Dicklyon (talk) 18:30, 3 May 2009 (UTC)

Dick, That's correct. There has been nobody else but myself in the last two years who has advocated the approach that was adopted by Leibniz and Goldstein. It is not my approach. I didn't invent it. I did the classical mechanics course many years ago and it dealt with planetary orbits as per Goldstein. Centrifugal force is independent of centripetal force and in the case of when gravity is the centripetal force, the two operate in tandem to yield hyperbolic, parabolic, or elliptical orbits.

You are one of the few who has actually followed up Goldstein and who appears to have comprehended the Leibniz approach. But you are now behaving as badly as Isaac Newton in that you are trying to mask Leibniz's approach. But unlike Newton, you are trying to get it all tangled up with fictitious forces and rotating frames of reference when there is no need to do so. Newton on the other hand messed it all up by making a general equality between centrifugal force and centripetal force and calling them an action-reaction pair as per his 3rd law of motion.

I'm going to go back to the talk page on the other article and list the different approaches to what is essentially one topic. David Tombe (talk) 18:41, 3 May 2009 (UTC)

There is no such thing as reactive centrifugal force (yet again) -- Article really should be deleted

The central premise of this article is: "Centrifugal force is an actual force as it is the 'equal and opposite reaction' of the centripetal force -- and that is another perfectly valid way of looking at it." That is a very very common misunderstanding, but it is a misunderstanding. It is not a valid way of looking at it.

To be short and sweet about why: It's a misinterpretation of "F=ma". Just because the vector "ma" is equal to the vector of the net force (F), doesn't mean that "ma" is a force. In some disciplines, it has been useful to write it as "F-ma=0" which further makes "ma" look like a force. This suggests that the sum of forces on anything is always zero (which is incorrect). The thinking goes that since the centripetal force is real (which is correct) then to make the sum of forces zero, the centrifugal force must be it's "equal and opposite reaction" to balance off the real centripetal force. Right? Nope, that is not true because the sum of forces (net force) doesn't need to be zero. The article is also a big misinterpretation of Newton's third law. But, I don't want to belabor an explanation as to why the premise is so incorrect. I could, but I will spare you. The community of solidly-founded physics professionals will support me on this.

Besides the bad premise, the article also is almost entirely unreferenced. The single reference appears to be about relativity while the article is about classical mechanics. The example in it also has reliability issues (remarked in previous discussions). This shortness of references is most assuredly due to the difficulty of coming up with reliable references in support. The article is basically WP:OR.

The article mentions a bunch of uses and examples of centrifugal force. These are all immaterial and off-topic to the main (extraordinary and dubious) claim that centrifugal force is something other than the inertial opposition to an accelerating frame (which is itself the result of non-zero net force). Ignoring that frippery, the article contains very little on-topic heft. That remaining on-topic material should be deleted not merely for its dubiousity and uncitability, but for it's outright wrongness. In short, the whole article really should be deleted.

User276 (talk) 08:09, 24 July 2012 (UTC)

You, or anyone else, can nominate it at Articles for Deletion, if you wish. Then, other users will discuss whether or not they support your nomination. Based on the comments made by other editors and the arguments in those comments, an administrator will close the discussion in 7 days or so (more, if required) and, if the community consensus is to delete the page, it will be deleted.  dalahäst ^{(let's talk!)} 08:14, 24 July 2012 (UTC)

User276, it's clear to all that the old concept of reactive centrifugal force is not a preferred way of looking at things these days, and is not what is usually meant by centrifugal force (rotating reference frame). That's why we have the summary-style article centrifugal force to contrast them. But I don't understand your "no such thing" comment. Cannot the force of the moving object on the object that is putting a force on it be called the reactive centrifugal force? It does seem to be called that by some (more in older sources). I add a few more refs. Dicklyon (talk) 07:41, 25 July 2012 (UTC)

Hi Dicklyon, et al,

Questions in science aren't resolved by opinions about whether a concept is old or new or preferred or not preferred, right? They are, of course, resolved among scientists with regard to reliability, i.e. how well they predict experimental results. However, maybe questions in WP includeability are? Or aren't? Anyway, we do know that reliable references are required. That seems straightforward enough, except how do we know what references are reliable? Here, it is up to the editors' knowledge and judgment to make that distinction. It is also sometimes necessary to make reasoned arguments as to what refs are reliable by arguing about the actual science. I am arguing here that any ref that asserts "reactive" CF is not reliable.

Like you said, the refs calling it "reactive" tend to be older. That makes sense because science is all about casting off unreliable or less reliable ideas about the nature of nature. Science does this all the time. Science is a continuous improvement process. Sometimes, modern writers look to the old refs and repeat their errors. That, along with actual misunderstanding on the modern writers' part, is what is behind the modern refs' usage of "reactive". I guarantee though, that among modern PhD physicists, you won't find one who asserts the "reactive" explanation. We must consider all "reactive" refs to be unreliable.

Some of the factors that lead to confusion are:

1) The very unfortunate term "fictitious" force. There are better terms that don't connote unreality. The "fictitious" force is a real "thing", it's just not produced by the Fundamental Forces in the Standard Model. The thing called "fictious" is just the "ma" part of F=ma (or F-ma=0). Still real, just not a fundamental force.

2) The fact that there are force pairs all over the place in a circling-weight-on-a-string system and in the myriad other examples of CF. It is easy to confuse these force pairs with the actual "source" of CF.

3) There is a lack of discernment in the use of the word "reactive". The general meaning that something happens "in turn" and "in response" to something else is muddled into the more specific meaning here: "that centrifugal force is an actual force as it is the 'equal and opposite reaction' of the centripetal force -- and that is another perfectly valid way of looking at it." This specific meaning is always wrong. The general meaning can be right, but intermingling it with the specific meaning can incorrectly make the specific meaning look correct when it is not.

If the idea that centrifugal force is "an actual force as it is the 'equal and opposite reaction' of the centripetal force" is included, it should be in a historical context or in a "Common Misconceptions" section of the main (and single) article. There it can be pointed out exactly why it is a superseded concept.

User276 (talk) 17:31, 9 August 2012 (UTC)

The fact that it has largely been supplanted as the preferred concept doesn't mean it doesn't exist as a real force. Don't we already discuss this in the history of the conception of CF? I linked that in the lead. Dicklyon (talk) 17:42, 9 August 2012 (UTC)

True, the fact that it has largely been supplanted as the preferred concept doesn't mean CF doesn't exist as a real force. But, the fact that CF doesn't exist as a real force is true independently!  :-) But all this really depends on what a "real" force is of course. Calling it a "real" force implies that it is one of the fundamental forces in the standard model. That's the modern usage of "real force" among the most reliable practitioners (Physics PhD's, etc.). So, in this definition of "real" force, CF most assuredly does not exist as a "real" force. Although, CF is indeed a real "thing", just not a "real" force. The real thing that it is is the "ma" part of "F=ma" (the sum of all "real" forces = ma)

The idea that CF is a "real" force and that it is just the "equal and opposite" to the centripetal force belongs in the dustbin of "Common Misconceptions" in the main article only and nowhere else. People buy into it in the modern day mostly because of "confusion number 2" above. They don't do a full and correct analysis of the forces and their reactions (the "general" sense - beware "confusion number 3").

User276 (talk) 18:48, 9 August 2012 (UTC)

I don't understand or agree with Calling it a "real" force implies that it is one of the fundamental forces in the standard model. Do you have a source for this concept of "real force"? Dicklyon (talk) 18:53, 9 August 2012 (UTC)

Source? How about Standard Model or Beyond the Standard Model? When I was a kid in the '70s, the (four) forces were Electromagnetic, Strong, Weak, and Gravitational. Now that Electromagnetic has been tied to Weak, it's called "Electroweak". All these forces are carried by particles. For example, in the case of the Electromagnetic forces that particle is the photon. All forces, chemical bonds, etc. - everything that can "push" on something else is done via particles carrying these forces. In some cases like gravity, experimental evidence is thin, but the point is that these are the only "real" (non-"fictitious") forces. These are the things that sum up to go into the "F" side of "F=ma". The "ma" side is the resulting acceleration. I don't like the term "fictitious" either (see "confusion number 1" above). Like I said, a "fictitious force" is a real "thing", just not a "real" (or non fictitious) force. I only use the term "real" as the opposite of that awful term "fictitious" as much as I dislike how they incidentally (and incorrectly) imply existence or non existence.

User276 (talk) 20:18, 9 August 2012 (UTC)

String-Ball-Post diagram concept is so incredibly wrong...

The diagram (and whole article) purports that the "equal and opposite" of the centripetal force (CPF) is the centrifugal force (CFF). But the CPF's "opposite" (the force keeping the end/center of the string from accelerating) is actually the force on the post. The post exerts a force on the string and the string exerts a force on the post.

The post would move if the only force on it was the string. What really happens is the post puts a force on the earth and the earth accelerates accordingly inversely proportional to its mass, which of course makes the post appear fixed (a mistaken idea leading to all kinds of misconceptions). On the other end, the post puts a force on the string, the string puts a force on the ball, and the ball accelerates inversely proportional to its mass. The system is really two "fictitious forces" ("mA" and "Ma") connected by "real" (standard model) forces (string-post-earth) resulting in zero net acceleration.

The diagram is a major error in concept and it supports a major error, which is the whole article. The article must either be (1) deleted, or (2) at a bare minimum it should change its perspective from asserting this as a valid description to instead demonstrating an example of an invalid description, why it's invalid, and its history.

User276 (talk) 19:49, 9 August 2012 (UTC)

I'm not following you on what's invalid about it. Can you find a source that explains why the concept of reactive centrifugal force is invalid? Dicklyon (talk) 20:18, 9 August 2012 (UTC)

Take a look as "Confusion number 3" in the previous section regarding "reactive", we all really need to be more specific.

All this is indeed a hard nut to grasp. I'm an engineer and I really only started to understand it a few years ago when I started discussing it with a physics professor friend. I started out believing this "reactive" perspective too, but it just doesn't hold up. The "fictitious force" model is indeed harder to grasp, but that's no reason to be attracted to a simpler, but wrong, model and then call it "equally valid".

You are defending an article that essentially says "The sun goes around the earth" and you want sources saying otherwise? Sources abound! Why don't you go get those sources? You'd learn something in the process. If instead you want to only seek out sources that support validity, you can find them. But, like I said, reliability of sources can only be estimated by applying the expertise of editors. And, editors who actually know their stuff know that any source asserting validity is not reliable. I've made arguments regarding the invalidity of the article as have many others before me.

The article amounts to scientific quackery as it stands and I can't spend any more of my time educating you or anyone as to why it is. Please review the explanations here and in the above sections, and/or go out and educate yourself some more on the matter. I will be making "bold" edits soon to correct some of the most egregious problems if someone doesn't pipe up and get to it first.

User276 (talk) 21:11, 9 August 2012 (UTC)

Nomination for deletion.

This article is beyond hope in my opinion. It can only be "fixed" by injecting a lot of weasel wording to talk around the outright scientific quackery it asserts. At some point, I will nominate for deletion based on the following concerns:

• This article presents a long discredited view about the nature and origin of centrifugal force. The view is put forward as if it is another also-valid view on the subject, but it is not scientifically valid. It contains numerous fundamental errors. The material is presented as factual, when it is more historical in nature - as in the history of scientific ideas that are now in the dustbin. Attempts to find reliable and modern references have failed. See discussion for the long history of complaints about lack of validity. The subject is largely duplicated in the main Centrifugal Force article where its errors can be more readily corrected. The subject is notable for mention as a "Common Misunderstanding" in that main article, but it is not notable for its own article.

Consensus is needed of course, so please pipe in below. Remember, this subject requires some real knowledge, some real discernment, and some real head scratching to really really understand. I am a knowledgeable long-time practitioner, yet just a few years ago I felt it was a valid perspective and I preached it with bluster. I was wrong. The subject doesn't have to go away, just this article. The subject can remain in the "main" article and be modified there to correct its errors there.

User276 (talk) 01:19, 10 August 2012 (UTC)

Wait, you're a long time practitioner (of what?), and until a few years ago preached it with bluster? Now your eyes have been opened, you've cast out the lies, and want us to come along with you? Seems too much like religion to me. Dicklyon (talk) 04:21, 10 August 2012 (UTC)

My colorful language was irrelevant. Please focus on the subject at hand here. If you want to argue against deletion, please do that directly and with good evidence. Let's make the chit chat somewhere else or in some other section. User276 (talk) 05:35, 10 August 2012 (UTC)

Jumping the Gun

As a college instructor in Physics, I am just as concerned about the potentially misleading term "centrifugal" as anyone else. However, this article does not contain any outspoken nonsense. The reader simply must take care to distinguish carefully what is and what is not said. Deleting the article at this point would be jumping the gun.

There is room for improvement. One could tabulate the forces acting on the various objects in a more systematic manner. Also, the statement that "the two forces upon the string are equal and opposite, exerting no net force upon the string, ..." is technically not quite true, since the string's center of mass is rotating and must have a non-zero net force acting on it. (But if the mass of the string is negligible, so is the net force on it.)

Let me try to vindicate the article as is, using basic Newtonian mechanics.

F1: Inward force by string on the spinning mass. ("Centripetal force")

F2: Outward force by the spinning mass on the string. ("Reactive centrifugal force")

F3: Inward force by the pole on the string. ("Post reaction force")

F4: Outward force by the string on the pole.

(F5: Inward force by something else on the pole, to keep it balanced.)

Forces F1 and F2 cannot exist without one another, due to Newton's third law. The same is true for forces F3 and F4.

In the inertial frame of reference, force F1 is the only force on the spinning mass, which is therefore not balanced. At this points many people incorrectly introduce a "centrifugal force" on the spinning mass, believing it should be balanced. This is the most common misconception, but it is not found in the article.

Forces F2 and F3 act in opposite directions on the string. If the string has negligible mass, F2 and F3 must balance to prevent the string from being pulled outward. The forces constitute the tension in the string.

Consider a hammer thrower. If the cable is not strong enough, it would break due to the tension in it; this proves the presence of F2 and F3. Toward the end of the swing, the hammer thrower has difficulty staying in place; this is due for force F4. — Preceding unsigned comment added by Arjenvreugd (talk • contribs) 02:12, 26 November 2012 (UTC)

"Centrifugal" is not misleading at all. It simply means "center fleeing". It just specifies a direction of something. "Centripetal" similarly only means in a direction toward a center. Too many people trying to "get it right" think there's something "fictional" about "fictitious force" (AKA pseudo or d'Alembert force). They've been told by their high school and college instructors that there's nothing fictional about "centripetal force", so they substitute "centripetal" when they're thinking "away from the center". They try to avoid looking dumb, but they underscore their ignorance instead.

The real way to "say it right" is to say "centrifugal pseudoforce". It's the "force" part of the term that's misleading, not the "centrifugal" part.

Montyv (talk) 03:52, 31 May 2014 (UTC)

Does the fictitious force supplant the reactive force?

The term "reactive centrifugal force" is not used for probably many reasons. The reaction to a centripetal force is often centripetal, not centrifugal. This is quite evident in the case in the moon and earth orbiting the barycentre, as pointed out by G. David Scott in the article that I have cited (added to the authorities listed in the first page). It is also very confusing.

The article as it stands is not bad but it really perpetuates the confusion. To suggest, for example, that the "reactive centrifugal force" has been "supplanted" by the fictitious centrifugal force is mindboggingly confusing. The article strives to make it clear that the reactive centrifugal force and the fictitious centrifugal force are very different phenomena. That would imply that one does not replace the other. So why confuse everyone by suggesting that the fictitious force has replaced (supplanted) the reactive force?

I am proposing that the first sentence of the second paragraph be changed as follows so that the intended meaning is clear:

from: "The concept of reactive centrifugal force is seldom used in modern physics and mechanics, having been largely supplanted by the concept of centrifugal force as a fictitious"...

to: ""The concept of reactive centrifugal force is seldom used in modern physics and mechanics. The term "centrifugal" is usually used in reference to the fictitious"....

Contrary to Dicklyon's contention that my proposals are mean-spirited I can assure you that my goal here, as in all my WP activity, is to improve the quality of the information for readers. AMSask (talk) 04:15, 12 January 2014 (UTC)

Where did I suggest your proposals are mean-spirited? I'm not loving this change, but I don't see the point of it. What was supplanted, as it said, was the concept; not the force. Dicklyon (talk) 06:31, 12 January 2014 (UTC)

You said my change was ill-motivated. Perhaps you meant ill-conceived. AMSask (talk) 07:05, 12 January 2014 (UTC)

Where you removed the text "is directed in the direction from the center of rotation to the rotating mass" you said "Removed reference to apparent direction". That removal is badly motivated since there is no mention of apparent direction in there anywhere; just an actual direction. Then you changed the discussion about the comparative concepts, reactive centrifugal force and the fictitious centrifugal force, to a statement about the usage of the word centrifugal: "The adjective 'centrifugal' is most often used in relation to a different phenomenon". But it is not so much a different phenomenon as it is a different conception of the same phenomenon, about forces involving rotation. This wording change seemed badly motivated, too, but I agree that maybe badly conceived would have been a better description of the problem. I don't mean that your motivations in editing are bad, just that this edit has no good reason. Dicklyon (talk) 19:33, 13 January 2014 (UTC)

They are NOT the same phenomenon nor are they a different conception of the same phenomenon!!! This is the problem. The reader of this article may well think that! It is not the case. See my response below to your other comment.AMSask (talk) 23:15, 13 January 2014 (UTC)

You are expecting the reader to discern what you perceive to be a difference between the concept of a force and the force itself? I don't think there is a difference, but if there is it is not going to be understood by the reader. CF does not replace or supplant RCF. It can't, of course, because it is an entirely different phenomenon. The article should say that. It says the opposite. AMSask (talk) 07:05, 12 January 2014 (UTC)

I don't understand you here. I am not expecting the reader to have anything to do with my perceptions. But there are historically different ways to conceptualize the forces in rotating systems, and this is what we're contrasting. Saying they are different forces might miss the point, as they can't both exist simultaneously, as they are in different systems. I think "entirely different phenomenon" goes too far in contrasting these concepts. Yes, they are different; but "entirely"? They are closely related. Dicklyon (talk) 19:33, 13 January 2014 (UTC)

How is the so-called reaction force to a centripetal force (RFTCPF) related at all to the fictitious centrifugal force (CFF)? The CFF is not even perceived as a reaction force to any force, real or fictitious. It has no physical source. It is not a Newtonian force. The RFTCPF is a real force that is in reaction to a real force and has a physical source (ie. originating in some body due to gravity or electromagnetic effect). Furthermore, the RFTCPF and the CFF act on different bodies and often in quite different directions (in relation to the direction from the center of mass of the bodies they act on, or are perceived to act on, and the center of rotation). What do they have in common?AMSask (talk) 23:15, 13 January 2014 (UTC)

The relationship is actually described in a table in the article. If the rotating reference frame is rotating about the center of rotation of the mass, then I think the two have identical formulas and magnitudes and directions (I'll have to check the conditions and verify when that's true; certainly when the motion is circular). They are different points of view on the same effect, the effect that relates rotation and inertia. Dicklyon (talk) 04:55, 14 January 2014 (UTC)

How are they just different points of view on the same effect!!?? There is a fundamental difference between the reaction force to the centripetal force and the centrifugal force: the reaction force has a physical cause (gravity, electromagnetic) whereas the centrifugal force does not. The reaction force does not arise because of rotation and inertia. It exists whether there is rotation or not. If two bodies in gravitational orbit stop rotating the forces between them do not disappear. The forces between the bodies do not change. As a result the bodies accelerate toward each other. The centrifugal force, however, disappears. So, again, what do they actually have in common?AMSask (talk) 06:51, 14 January 2014 (UTC)

Rotation. Two bodies falling toward each other without rotation don't have a force directed from a center of rotation. Seems pretty consistent. Dicklyon (talk) 07:25, 14 January 2014 (UTC)

That is true. Two bodies falling toward each other without rotation don't experience a force directed away from the center of rotation. But bodies falling toward each other with rotation don't experience a force directed away from the central point either. So the forces between the bodies do not change. The only thing that changes is your terminology? Is that your point? So you agree that without rotation it is correct to characterize the gravitational forces on each body as being directed toward the centre of mass of the two body system, but not when they are rotating? What changes with the rotation? AMSask (talk) 14:30, 14 January 2014 (UTC)

I think we agree that the gravitational force between two bodies is always along the vector between them. Each feels a force toward their center of mass. When there's circular rotation, that's the same point as the center of curvature of motion of either body. When elliptical or other non-circular orbit, the center of rotation moves and is not at the center of mass. Sometimes people do explicitly account for a "centrifugal" component that is less than the whole force of gravity, and is along that line. It does get a bit messier, and terminology is not always consistent about how that's done. Dicklyon (talk) 19:19, 15 January 2014 (UTC)

I would caution against putting that kind of statement into the article. There are two different centres of curvature for an elliptical orbit, one for each body. And they keep changing. Neither can be an inertial point. There is only one centre of rotation (i.e.located at the focus of the ellipse). The force on the bodies are directed to the centre of rotation, not the centre of curvature. AMSask (talk) 19:52, 15 January 2014 (UTC)

Please Reword

The first paragraph needs re-wording. It is not clear which force is on which object. It is the sentence: "In accordance with Newton's third law of motion, the rotating mass exerts an equal and opposite force on that object, which is directed from that object toward the rotating mass". Better would be something like "...the rotating mass exerts an equal and opposite force acting on that object and is directed towards the rotating mass". Also the use of "rotating mass" is confusing here; it suggests a spinning object like the "rotating earth". "object moving in a circular path" may be better. Can you please re-write? I like the "Jumping the Gun" comment. It clearly shows which force is on which object and outlines the action-reaction pairs. The same should be done here. Perhaps edits by various disagreeing writers has rendered this article confusing. It would be good to have a clean consistent approach.

— Preceding unsigned comment added by 67.170.141.69 (talk) 21:29, 24 May 2014 (UTC) 

Your best bet is to ignore the whole article. It's garbage. Perfectly pathological science.

Montyv (talk) 03:02, 31 May 2014 (UTC)

Pathological science: There's still no such thing as reactive centrifugal force.

Beware the authoritative, but unreliable reference. There is no subject that I know of more in need of the judgement of very knowledgeable editors than Centrifugal Force. I see many arguments above based on the "argument from authority" fallacy. It's our duty to reject the argument that "some prestigious institution published 'X' 50 years ago, therefore 'X' is includable". This even applies to more recent publications. 'X' is simply not includable if it's dubious, even more so if it's outright wrong. And, if 'X' is dubious or wrong by the judgement of knowledgeable editors, then references that say 'X' are unreliable and 'X' is not includable.

This includes Newton himself. Newton is not a reliable reference. We see farther than he did because we stand on his (and others') shoulders. Pseudoforce wasn't even a real concept until d'Alembert 100 years after Newton. There are too many good, modern perspectives and references debunking the view of Centrifugal (Pseudo)force which says it's a fundamental-force reaction "paired" to a centripetal force (as in the shoddy and ambiguous "forces come in pairs" - gag me). There is no excuse for repeating this pathological science as if it was reliable and real when we know damn well better.

This may appear to some to violate the infamous (and misleadingly simplistic) "WP:verifiability, not truth" maxim. But if you read it carefully, you will see that "verifiability" requires reliable references. And there is no way to determine reliability but by the judgement of knowledgeable editors.

Beware also, the difference between a "knowledgeable editor" and a merely "persistent" one. The idea of "reactive centrifugal force" has been perpetrated on Wikipedia largely by one particular persistent editor who is always around to push this pathology. He has a "sciency" degree, so he can speak with the feel of authority, but somehow he got this bad idea in his head and it won't go away. And somehow, he's always there.

This article is shameful. It needs to be deleted outright. Get it over and done.

Montyv (talk) 02:55, 31 May 2014 (UTC)

If you think the article is so shameful, then stop talking about it and put it up at WP:AFD. Let's see what happens.

With regards to your "dubious" tags, I don't think we are on the same page when we are talking about the "reactive centrifugal force". In my understanding the D'Alembert principle and Newton's Third Law are completely different. So that we can clear up the "dubious" tags and perhaps find better wording, I'm going to try identify where our difference of understanding is. Let's start by looking at where we have both principles present, but not looking at circular motion in particular for now: an object in an elevator going up. When the elevator first begins to accelerate upwards, from the perspective of the outside stationary frame their are two forces on the object - gravity (F_g) and the contact force of the floor on the object (F_1). Because the contact force on the floor is greater than the force of gravity (F_1>F_g), the net force is non-zero and upwards so according to Newton's 2nd law (F=ma) the object accelerates upward. If we instead wanted to look at this from the perspective of the accelerating frame of the object, D'Alembert says that we can transform an accelerating rigid body (the object here) into an equivalent static system by adding the so-called "inertial force" (F_i) acting on the object. The inertial force is given by F_i=-ma. This inertial force is why we say we feel "heavier" when an elevator starts going up. In the Newtonian definition of forces, there is no additional force pushing us down, but the feeling is an artifact of us describing the motion from an accelerated frame. Are we in agreement so far? If not, where do we disagree?

On to part 2 of the example. According to the Newton's 3rd law, the real forces all have to have equal but opposite pairs. The 3rd law counterpart of F_g is the force of gravity of the object on the earth, and the counterpart of F_1 is the contact force of the object on the floor (F_2). These forces exist regardless of whether we are describing motion in the stationary frame or the accelerating frame. F_2 is equal in magnitude to F_1, but points down in the opposite direction. Also F_1 acts on the object, but F_2 is acting on the elevator floor. So if we are applying F=ma to the object, or drawing a free-body diagram of the object, F_2 isn't part of that picture since it is not acting on F_2. We also can't talk about F_1 and F_2 "balancing", since again they are acting on different objects. In a lot of textbooks, they would say that F_1 and F_2 are an action-reaction pair, but trying to identify which one is the action or reaction, implying some kind of causality, is impossible since they occur simultaneously and are part of a single interaction (neither force exists without the other). Are we on the same page, and if not, where do we differ?

Taking this as an analogy to circular motion, F_1 is analogous to the centripetal force, F_i is analogous to the centrifugal (pseudo)force, and F_2 is analogous to the reactive centrifugal force. Like F_i, the centrifugal (pseudo)force acts on the object, is frame dependent, and vanishes in the stationary frame; like F_2, the reactive centrifugal force acts on the source of the centripetal force, is not frame dependent, and appears in the stationary frame. Some relatively modern sources that mention this distinction between the centrifugal (pseudo)force and the reactive centrifugal force are: John Roche (2001) "Introducing motion in a circle" Physics Education 43 (5), pp. 399-405; Yukio Kobayashi (2008) "Remarks on viewing situation in a rotating frame" Eur. J. Phys. 29, pp. 599-606. --FyzixFighter (talk) 16:00, 31 May 2014 (UTC)

Hi there FyzixFighter,

You're not the one I was alluding to by the way. I shouldn't have pointed a finger the way I did, it was uncivil. Sorry.

I like that you've decoupled rotation from acceleration. The essence of the centrifugal "force" question is indeed inside the linear acceleration example. After all, if a linearly accelerating object in free space (like a rocket with near-infinite Isp) is given a very very slight rotation rate (around an axis perpendicular to the acceleration), that acceleration becomes "centripetal". The "center" would likely be "moving", but that's easy to fix with a switch to a new (also non accelerated) reference frame. So, a linear acceleration caused by a non-zero net (fundamental) force* is really the same situation as a centripetal acceleration caused by a centripetal (fundamental) force when the radius is very long and/or omega is small. (*pretend it has a veeery slow rotation rate if you wish)

I also like how you've been careful say that a force is real or pseudo (if it wasn't clear by context). That's the kind of clarity the article needs more of.

I have more to say, but it's taking me a while to compose. I wanted to at least get some response out quickly. Thanks for your well ordered response. I'm optimistic.

Montyv (talk) 04:03, 1 June 2014 (UTC)

The first "dubious" marker I made can probably be resolved in large part by being specific about the type of force. To me, it implies (although it's not clear) that both are supposed to be "real". If so, then the article is calling CF "real" and I think you might agree that's a dubiousity problem. I called it OR because of lack of citation. Less importantly, it's also OR-ish because it interprets Newton - rather than paraphrasing a secondary source, it makes itself a secondary source.

The second "dubious" marker I made was again because of ambiguousness of what type of "force". Lack of clarity opens up for multiple interpretations, some of which are dubious.

By the way, I've been trying like crazy to download reference 5 from archive.org and I've been having trouble with Java on my browsers. Do you have it? Have you had any luck from archive.org? I'm really curious now what those refs actually have to say. I saw the 1884 book. The three remaining refs (other than ref 5 & the 1884 ref) were all behind a paywall. Do you or anyone else have copies of the pertinent pages of those refs to share in fair use so we can see what they say? Technically, a ref doesn't have to be internet-accessible and free of course, but it does help a lot in situations like this.

(More to come still.)

Montyv (talk) 04:50, 1 June 2014 (UTC)

That's odd that you're hitting a paywall. Do these links work for the first two references: Mook and Vargish, 1984, Brar and Bansal, 2004. I've relied on google books to get a look in most of these books. Ref #4 is behind a paywall, but you can at least get a preview of the first page of the article. Ref #1 and #2 are actually good cites for both of the comments you marked as dubious. I too can't seem to get access to ref #5.

I mentioned the linear acceleration example as merely an analogy. It's a purely linear case where you have a real force of the floor on the object, a fictitious/D'Alembert force in the opposite direction to make the accelerated frame look like a static frame, and a real force also in the opposite direction of the object on the floor. Let me take that analogy and be more explicit in how this looks for rotational motion. Imagine a space station that is rotating to simulate gravity (a la Space Odyssey 2001), so that the outer wall of the station is the "floor" of its inhabitants. From the perspective of an outside, stationary observer the wall/floor exerts a centripetal force, F_1, on an inhabitant. By Newton's 3rd law, there is also a force, F_2, that the inhabitant exerts on the wall/floor that is equal and opposite to F_1. In this case that means that F_2 is radially outward, and can be described as "centrifugal". From the perspective of the inhabitants, they see both F_1 and F_2, but because their observations are within an accelerated frame, they have to add a centrifugal (pseudo)force, F_c, acting on themselves to make the dynamics look like a stationary frame. This is the primary and most common usage of the term "centrifugal force" in physics, to refer to this fictitious/inertial/D'Alembert/pseudo-force. That's what the article centrifugal force (rotating reference frame) is meant to describe. The other two forces, F_1 and F_2 are real and form a action-reaction pair. F_1 is what we commonly call the "centripetal force". Physics texts generally don't spend a lot of time on F_2, usually just noting it as the 3rd law corresponding force to the centripetal force. But there are a few sources that call this a "centrifugal force" or the "reactive centrifugal force" since it points away from the axis of rotation (for example Acceleration and force in circular motion, which does the space station example). That's the force this article is meant to describe. Both F_2 and F_c are technically centrifugal. But we can describe their differences as follows: F_2 is a real force that both the stationary and rotating observers will see; F_c though is a pseudoforce since it vanishes in the stationary frame. F_2 acts on the wall/floor in the space station example; F_c acts on the inhabitants. F_2 has a 3rd law corresponding force (F_1); F_c has none.

Does this explanation make sense? If there's disagreement, where do we disagree in this example? --FyzixFighter (talk) 19:33, 1 June 2014 (UTC)

You agree that F_2 is a pseudoforce, right? All the evidence points to the idea that the term "action" (or "reaction") may indicate either a force or a pseudoforce. "Action" is a superset of the two "types" of force. Here's why: In the space station example, if F_2 isn't a pseudoforce, it must be a fundamental force, but then the object moving in a circle would have zero net fundamental force acting on it and would be moving in a circle by magic. So F_2 must be a pseudoforce, and if F_2 is called an "action" (or "reaction"), then "actions" must include both pseudoforces and forces.

F_2 is a result of (or even a "reaction to"(!)) the (centripetal) acceleration ma, which itself is a result of (or "reaction to") the nonzero net fundamental force (NZNFF) F_1 . So, the 3rd law's "action-reaction" phraseology must be talking about the superset of forces and pseudoforces. Call a pseudoforce a "reaction" if you wish, but it's still a pseudoforce, right?

Your idea that F_c is sitting there by itself is an interesting one. I'm skeptical of it, but I'll have to get back to you on it because it requires thinking.

Montyv (talk) 00:11, 4 June 2014 (UTC)

I just re-read your last response and noticed you did call F_2 a real force. That is a problem for the reasons I gave above. It's something the "pro reactive CF" and "anti reactive CF" camps need to resolve before making progress. Otherwise, the removers of text suggesting "real force" would surely be at edit war with those advocating elimination of such text.

I can certainly see how CF (which is really the same as the inertial response to a linear acceleration) can be considered as a "reaction" to a real force. It's an instantaneous (simultaneous) "reaction" indeed. Pseudoforce is (-ma) and becomes present as a "reaction" to the acceleration (ma/m). It's as if it's nature's way of implementing the 1st law. The acceleration itself is a simultaneous "reaction" to NZNFF. So, as long as the explanation is perfectly clear that that's why "reactive CF" is called "reactive", that would be technically correct. I have a feeling that's not the intended meaning though. I can't tell what the intended meaning is because the article is so gat-danged ambiguous and vague.

Anyway, as far as I can figure out, F_2 and F_c are one and the same things, both pseudoforces, both vectors pointing in the same direction and with the same magnitude. They both act at all points inside the object at once, and they both act as though they are through same point on the same object (its center of mass). Also, they aren't the same exact thing because they look and act alike, rather they are the same thing because they just really are the same thing, i.e. they're not twins occupying the same space at the same time.

Montyv (talk) 04:58, 4 June 2014 (UTC)

(after ec) No, F_2 is a real force. "Actions" or "Reactions" as the terms are used in Newton's 3rd law only describe real forces. The only pseudoforce here is F_c. The key flaw in your argument is when you say that F_2 balances F_1 (giving a zero net force on the object/inhabitant). However, this cannot happen because F_2 isn't acting on the object/inhabitant. That's why I tried to be very clear about what forces are acting on what objects. When we sum up the forces to get F_net, we only include to the forces on that object. Since F_2 does not act on the inhabitant, then it cannot balance the force of F_1 on the inhabitant. F_2 is the force that the inhabitant exerts on the wall/floor of the space station. As Roche points out (in the article I mentioned above) when talking about these forces, they "are equal and opposite here but do not balance because they act on different bodies." Only if we were doing the forces on the space station would we look at F_2, but then we would ignore F_1 which is a force on the inhabitants. F_2 is caused by the same fundamental phenomenon that causes F_1. We can source this relationship and qualities of an action-reaction pair of forces to pretty much any intro physics textbook (eg, Resnick; Halliday; Krane (1992). Physics, Volume 1 (4th ed.). p. 83). F_c is all by itself because it is a pseudoforce, therefore it has no 3rd Law pair. --FyzixFighter (talk) 05:21, 4 June 2014 (UTC)

Additionally, F_c and F_2 are only the same magnitude when the object/inhabitant is stationary in the rotating frame. F_1 and F_2 will always be equal and opposite (but acting on different objects) by the 3rd Law, but F_c depends on the frame I'm sitting in. I've got at least two sources that back up this distinction (Roche and Kobayashi), do you have sources that support your statements about F_2 and F_c? --FyzixFighter (talk) 05:26, 4 June 2014 (UTC)

The floor of the station is the path by which the (fundamental) centripetal force F_1 is imparted to the inhabitant, causing the (centripetal) acceleration (ma/m). F_2 does of course push back on the floor by way of the (fundamental) electrostatic forces within the inhabitant and between the inhabitant and the floor. The source of F_2 is pseudo however (the inertial "pushback" of mass against its acceleration by a NZNFF). Montyv (talk) 14:44, 4 June 2014 (UTC)

Given this discussion, and still seeing no logic behind Montyv's objections, I removed the dubious tags. We can follow up here if necessary. Dicklyon (talk) 05:31, 4 June 2014 (UTC)

I recognize that "dubious" gets (some) people's backs up. I had been thinking about replacing it with "vague", but replaced it with "clarification" which seems to be the same thing but it shows the note via hovering. The distinction between CF being "real" (aka "fundamental") and being "pseudo" is the main justification for the existence of this article. Agree? Part of the problem is that the article dances around the fact that it is calling CF "real". See weasel words. Try to clarify that if you will (either of you or anybody). If you don't, I'll give it a try, but I don't have the the same perspective as you so it will be hard to avoid doing what you view as damage. Montyv (talk) 14:28, 4 June 2014 (UTC)

This article is based on a flawed concept: that the reaction force to a centripetal force is centrifugal. It isn't. As Prof. Scott stated very succinctly in his 1957 article: "The reaction to a centripetal force is not a centrifugal force but another centripetal force". This was precisely the mistake made by Mook and Vargish in their text when they refer to the earth exerting a centrifugal force on the sun. In a two body rotation, both bodies rotate about a common central point (their centre of mass) so the third law pair to the centripetal force of the sun on the earht is the centripetal force of the earth on the sun. It is a little less clear when the system consists of a rotating tethered mass. A rotating ball exerts a force on the end of the tether that is directed toward the rotating ball. You can call that a centrifugal force if you want to really confuse everyone. But the fact is that the tether is experiencing a net centripetal, not a net centrifugal, force. AMSask (talk) 20:53, 4 June 2014 (UTC)

There is no argument as to whether CF is fictitious or real. Rather, there are two different things called CF, one a fictitious force and one a real force; they have separate articles, as well as being compared in the summary-style article centrifugal force. And the concept of the "earth exerting a centrifugal force on the sun" is not a "mistake"; it's a point of view; that is, the force is in the direction from the sun toward the earth, which is termed centrifugal because it is with respect to the POV of the earth, even though it acts on the sun, toward the center of rotation. These distinctions can be clarified if needed, but need not be called "mistakes". Dicklyon (talk) 04:03, 5 June 2014 (UTC)

No argument as to whether CF is fictitious or real?! NO!!! That's the crux of the argument!!! Montyv (talk) 18:27, 5 June 2014 (UTC)

The article is saying that there TWO(!) different kinds of centrifugal force? WHAT?!! Dicklyon, you are highly mistaken!!! You are pandering an outmoded (by 200 years!) pseudoscience that happens to be supported by a number of naive-but-seemingly-authoratative unreliable references. That's why I warned in the first place to beware that kind of argument from authority. Montyv (talk) 18:34, 5 June 2014 (UTC)

Thesis hidden behind weasel words, vagueness, unclear refs.

Since this article is so fundamentally about calling such forces "real" (or "fundamental"), it needs to be much much more clear about that. If the arguments supporting "CF is fundamental/real" are so strong, they should be able to stand up to that light of day. As it stands now, the fundamental thesis of the article is hiding behind weasel words, vagueness, and unclear referencing. Montyv (talk) 14:44, 4 June 2014 (UTC)

I'd say the article is more about calling certain real forces "centrifugal" when they are applied by objects moving in curved paths (even when, with respect the object the force is applied to, it may be centripetal in some cases). I don't think there's anything fundamental about these forces. Dicklyon (talk) 04:06, 5 June 2014 (UTC)

There's no fundamental difference between the two situations of continuous circular motion vs. "curved path". The article is (incorrectly) alluding vaguely that there is. And then it again alludes vaguely with no explanation why that that presumed difference is somehow related to viewing centrifugal force as a fundamental force! (or as the also-vague "reactive CF"). Just more example of hiding behind non-specific fluff. Montyv (talk) 18:14, 5 June 2014 (UTC)

"Applications" section is off-topic fluff.

The applications section lists a number of real-world situations where centrifugal force in general is applied, but it says nothing about how "reactive centrifugal force" [sic] in particular applies or is related to each example. It's a lot of generic "mom and apple pie". Its attempts to make a connection to "reactive centrifugal force" are weak and particularly vague. It merely substitutes "reactive centrifugal force" for "centrifugal force". Then in the end it bizarrely says "These devices are commonly analyzed in the frame of reference of the rotating mechanisms, using the fictitious force version of the concept of centrifugal force." which seems to be saying the examples have little to do with ""reactive centrifugal force".

A stronger connection needs to be made between the examples and the subject of the article (whatever that subject is given that it's currently so vague). Without a stronger connection (and one that doesn't contradict itself!), the section is highly deletable.

Montyv (talk) 15:08, 4 June 2014 (UTC)

Yeah I've never liked that applications section either. If we do add anything, we need to make sure we have a good source that says it is an application of the RCF. I might have one, but I need to think on it. --FyzixFighter (talk) 03:11, 5 June 2014 (UTC)

The governor as described is not a very good example, but the clutch is. Dicklyon (talk) 04:16, 5 June 2014 (UTC)

So perhaps you can explain why it is the "reactive centrifugal force" that makes it work and not the "fictitious centrifugal force". The authors of the Centrifugal force (rotating reference frame) seem to think the centrifugal governor or clutch operates on inertia or the fictitious centrifugal force. Your reference to Anthony G. Atkins, Tony Atkins and Marcel Escudier (2013). A Dictionary of Mechanical Engineering. Oxford University Press. p. 53. mentions nothing about a reactive centrifugal force. This is not an authority for the statements made in the article. Retrieved 5 June 2014. AMSask (talk) 06:36, 5 June 2014 (UTC)

I have to agree with AMSask here. I don't find the provided ref very convincing in supporting the argument that the centrifugal clutch is an application of the reactive centrifugal force. Perhaps I'm not seeing it though. Could you explain what parts of that reference you feel supports the inclusion in the applications section. In the meantime I'm going to be a bit bold and try summarizing a different application that is mentioned in a journal article. --FyzixFighter (talk) 01:22, 6 June 2014 (UTC)

As with other situations, you can analyze it various ways. The reason the centrifugal clutch seems like a good example for the reactive concept is that the force applied by the shoes on the inside of the drum, which creates the friction to engage the clutch, is most easily described this way. It's not a case of what force makes it work, but only of how one chooses to describe those forces. In the flyball governor, the reactive force is all just tension in the rods (and in the springs if it's not just a gravity-loaded device); this reactive force is not so interesting in that device. Dicklyon (talk) 15:59, 17 June 2014 (UTC)

If I understand you correctly, you agree that the "force" which causes the clutch shoes to move outward against the spring force is the fictitious centrifugal force. However, you are stating that once the clutch shoes reach the drum the force that causes the shoes to engage the drum and grip the drum by friction is the reactive centrifugal force. This distinction is not very clear in the article so it is very confusing to the reader. Can you find any authority that makes this distinction? AMSask (talk) 13:20, 19 June 2014 (UTC)

You do not understand me well. I said nothing about any force causing the clutch shoes to move outward against the spring forces; but if you want to look at it that way, you can, in the rotating frame, and then you can invoke a fictitious force to describe that. I'd rather just consider the fact that the shoes are being moved in a circle, via a centripetal force applied by the spring; the reactive centrifugal force then stretches the springs, until the shoes can't move out further, after which the drum supplies more centripetal force to keep the shoes going around, and the reaction to that force is a force of the shoes pressing against the drum, causing the friction that engages the clutch.

DickLyon: It seems to me that the real problem here is in trying to distinguish between the "pseudo force" that moves the shoes out and the "real reactive force" that you say stretches the springs. It is extremely difficult for the reader to discern a fundamental difference between what you insist are two distinct physical phenomena. Perhaps others will comment but I think you have captured the reason so many object to this article. By calling the reaction force to a centripetal force "centrifugal" you are simply confusing everyone including, possibly, yourself. In reality, all net forces are centripetal. All accelerations are centripetal. All outward motion is inertial (ie. due to the inability of the real forces to provide the centripetal acceleration needed in order to prescribe circular motion). AMSask (talk) 15:23, 20 June 2014 (UTC)

But this is the entire point of the set of articles on centrifugal force: to clearly distinguish these two different forces that people call centrifugal, one of which is a real reaction force and the other is a fictitious force, and how they relate to the centripetal force that makes an object move in a curved or circular path. If it is difficult to discern the difference, we need to work harder. I think the table in Centrifugal force is a good thing for you to review first. Dicklyon (talk) 16:09, 20 June 2014 (UTC)

You state: "The force of tension applied to the spring, and the outward force applied to the drum by the spinning shoes are the corresponding reactive centrifugal forces." What is the force of tension that is applied to the spring? The tension in the spring provides inward or centripetal forces to the shoes. There is no force pushing the shoes out. There is only the centripetal forces of the spring pulling the shoes in. The reaction to the force pulling one shoe in is the centripetal force pulling the other shoe in. There is no outward force. It is inertia that drives the shoes out. AMSask (talk) 05:16, 20 June 2014 (UTC)

Yes, that's more like it, except where you say "There is only the centripetal forces of the spring pulling the shoes in", that's true except for the "only", because there's also the corresponding reaction force that is stretching the springs. If not, what is stretching the springs? Your notion that "It is inertia that drives the shoes out" is fine, informally, but has no interpretation in terms of forces; in fact, the shoes are NOT being driven out; they only have centripetal forces on them. The reaction forces to those centripetal forces on the shoes are centrifugal on the springs and on the shoes. It's not that complicated. Dicklyon (talk) 06:04, 20 June 2014 (UTC)

DickLyon: The stretch of the spring is due to the masses on either end undergoing centripetal force. If you ignore the mass of the spring, which means essentially that the spring acts as a conduit of force between the two rotating shoes, then all forces are centripetal. This means that even the reaction forces are centripetal. AMSask (talk) 15:23, 20 June 2014 (UTC)

"The stretch of the spring is due to the masses on either end undergoing centripetal force" either means you agree, that the stretch of the springs is in reaction to the centripetal force that they apply to the masses, or you have some other notion of causality in mind. The spring would usually be said to cause the centripetal force that moves the masses in a circle, as opposed to "due to the masses on either end undergoing centripetal force", but in action–reaction pairs its not really very useful to try to say which is cause and which is effect. If you use an infinitely stiff spring, just a tight wire, it's the same: the mass pulls on the wire with the same, but oppositely directed, force that the wire pulls on the mass. At the other end of the wire, the reactive centrifugal force of the one mass is applied centripetally on the other, just like in the gravity two-body case. Not a problem except that you are bothered when the reactive centrifugal force is applied centripetally. Dicklyon (talk) 16:09, 20 June 2014 (UTC)

Your phrase: "when the reactive centrifugal force is applied centripetally" says it all. Clear as mud. AMSask (talk) 15:27, 21 June 2014 (UTC)

Yes, agreed, that's unclear; it is better to ignore the center-related direction at the place where to force is applied, and just go with reactive centrifugal force, which refers to the direction from center of rotation toward the body that is doing the pulling. Dicklyon (talk) 19:27, 21 June 2014 (UTC)

If that was the convention, then we should refer to both forces as centrifugal (i.e. in relation to the body that is doing the pulling). Who refers to the force of the earth on the moon (which is the reaction to the force of the moon on the earth) as centrifugal? AMSask (talk) 22:12, 21 June 2014 (UTC)

I don't know of anyone who would do that. Dicklyon (talk) 23:13, 21 June 2014 (UTC)

Why is that? It is the reaction force to a centripetal force. Why not call it a centrifugal reaction force then? AMSask (talk) 04:27, 22 June 2014 (UTC)

If the circular motion is uniform, the reaction force on the end of the spring to the centripetal force of the end of the spring on the shoe (which you want to call the reactive "centrifugal" force) is always less than the centripetal force on the end of the spring. It is equal only if the end of the spring is massless. It is never greater than the centripetal force on the end of the spring. It can't be because the end of the spring is always accelerating toward the centre. AMSask (talk) 15:27, 21 June 2014 (UTC)

Agreed. Dicklyon (talk) 19:27, 21 June 2014 (UTC)

Yes. Please explain that. That would be good. And better still, we should all not worry too much about this section. It's problems are just a symptom. Fixing this section is good, but it's also just nibbling around the edges. We don't want to fiddle with it too much at the expense of ignoring the pseudoscience at the core of the article. Montyv (talk) 18:47, 5 June 2014 (UTC)

The amended "applications" section is not really about an application of reactive centrifugal force. It is about the analysing tensions in a rotating rigid body. The tensions are in all directions. The net forces are all inward. The tensions within the body have to provide the centripetal force required to keep the body together as it rotates. But that hardly qualifies as an application, any more than a baseball, or a frisbee is an application of reactive centrifugal force. There are really no applications of the "reactive centrifugal force" because by its very nature it only exists as a tension and can never cause outward motion. This is in contrast to the application of the inertial centrifugal force. The centrifugal clutch is an application of the inertial centrifugal "force" because by spinning the shaft the clutch pads move outward (due to inertia, not force) and engage the surface of the cylinder and cause it to rotate. AMSask (talk) 19:58, 7 June 2014 (UTC)

Having just read the article on centrifugal clutch, I am drawing a picture of an inertial force making the inner shaft expand. When the inner shaft comes into contact with the outer shaft it exerts a centrifugal force on the outer shaft. The latter would be the reactive force, the subject of this article. Am I correct? But can we have a reactive centrifugal force in the absence of an inertial centrifugal force? The two act on different bodies, but are they really two different subjects? 83.42.238.255 (talk) 10:00, 5 September 2014 (UTC)

Reaction_(physics) Link

I removed the link to "Reaction_physics". That article is unreliable in that it refers to "forces" always having equal opposites when the term "action" allows for pseudoforces. The "Reaction_physics", would need to be clarified before it can be used as a ref or a link. Montyv (talk) 18:56, 5 June 2014 (UTC)

The removal of the link doesn't change the wording in any way. If you think the link should be in place, I think you can handle being without it while the matter is discussed (because there was no wording change). Also, according to WP:burden: Any material lacking a reliable source directly supporting it may be removed and should not be replaced without an inline citation to a reliable source. That means if you want to replace the link, you have to justify it. Now, to give you a hand with that, while you may not use a WP article as a ref, you may cut and paste a reliable ref from the linked article into this article. The emphasis of course is on reliable, merely "authoritative" doesn't cut the mustard. Montyv (talk) 19:04, 5 June 2014 (UTC)

If the Reaction_(physics) article was fixed to not be so vague (and also to be correct), the link to it would be perfectly fine. Montyv (talk) 19:14, 5 June 2014 (UTC)

Now to get down to the meat: As usual, it all depends on what's meant by "force". If "force" may mean "a fundamental force OR a pseudoforce" then it is okay to say "a force always has an equal-opp force opposing it". If "force" means only "fundamental force", then it is outright nonsense to say "a (fundamental) force always has an equal-opp (fundamental) force opposing it". It that were true, we would never get "F=ma", we would only ever get "F=ZERO(!)". Montyv (talk) 19:14, 5 June 2014 (UTC)

I've provided two sources, Roche and Koyabashi. some relevant quotes from the two sources that call the real (ie, not pseudo) centrifugal force a reaction force:

True centrifugal force exists only as a reaction to macroscopic contact or binding forces.

and

The term centrifugal force then has two meanings: one is the inertial force due to the rotation of the noninertial frame relative to the inertial frame and the other is the reaction force of the centripetal force to produce acceleration toward the center of rotation. The origins of these forces are different from each other.

The third law only applies to real/fundamental forces, and the error in your paraphrase of it is indicative of where your understanding is flawed. No one is saying that the 3rd law predicts "a (fundamental) force always has an equal-opp (fundamental) force opposing it", but what we the law does say is that "a (fundamental) force always has an equal-opp (fundamental) force". The forces in the pair are not opposing because they are not acting on the same object, hence the don't balance (result in F_net=0) even though they are real, equal and opposite. Again from those same references:

Centrifugal and centripetal force are equal and opposite here but do not balance because they act on different bodies.

and

The centrifugal force due to the rotation of the noninertial frame and the centripetal force act on the same point mass. The former force does not make a pair of action and reaction with any force, while the reaction of the latter force is the force exerted on the surroundings by the point mass.

A more general reference for this statement can be found in John Taylor's "Classical Mechanics" pg 17 (a fairly standard, modern physics text for classical mechanics)

According to the third law, the reaction force of object 2 on object 1 is always equal and opposite to the original force of 1 on 2.

Now, where are the references that support your view? --FyzixFighter (talk) 19:41, 5 June 2014 (UTC)

Thanks for your cool head in our reversion cycle. I see it as a sign of good will. I'll have to return the favor some day.  :-)
     So far, I've been able to look at the ref from PHYSNET MISN 0-17 by Signell. That ref is all well and good until it gets to saying "Newton's third law says that for every force there is an equal but opposite force". Then to clarify that it isn't talking about "F_1's pull on the post (or on the center of the space station)", it goes on to say "and the force equal but opposite to the centripetal force is called the centrifugal force". So, as so often the case, the way this source rephrases the 3rd law ambiqu-ifies the matter by being unclear about what "force" encompasses. That alone wouldn't make the source unreliable, but for the fact that one interpretation ("both FF and PF") is wholly correct and the other interpretation ("only FF") is wholly incorrect. Since the source can be interpreted either way, it is ambiguous and unreliable.
     We can disagree for the time being about ("only FF") being wholly incorrect, but that source also simply doesn't support your point (that CF is a FF) because it doesn't say "fundamental force" specifically. It just says "force" in a way that can also be read as "either fundamental or pseudo". It's ambiguous about the very point you would be trying to use it to support.
     I challenge you to find a reliable source that clearly and specifically says "CF is a fundamental force". That's what you need. Remember, the thesis of the article is that "CF is a FF". You (and supporters of that thesis) need to find (good) sources that support that. The burden is on you. If you can't find reliable refs that clearly support your thesis, well, you know what that means. To argue that your thesis is true because the other thesis is not proven true is Argument from ignorance, a logical fallacy. That is, I don't need to find refs to prove your thesis if false (particularly on a talk page), but you surely need (reliable) refs to support your thesis (particularly when you say it in the actual article). That said, I do find this all fascinating, and I am looking about for good refs myself.
     So, where are your reliable sources, eh? Like I said before, argument from authority doesn't cut the mustard. Ambiguous wording in sources doesn't cut it either. And neither does argument from ignorance. So, I am looking your sources over when I can find them. It is awesome fun!

Montyv (talk) 21:44, 5 June 2014 (UTC)

Quick question - what do you mean by "fundamental force"? Also, what is your definition of "pseudo force"? How do you distinguish between the two? For me one of the distinctions between real and fictitious forces is explained in this ref:

We call an apparent force such as this one a fictitious force because it is not a real force and is due only to observations made in an accelerated reference frame. A fictitious force appears to act on an object in the same way as a real force. Real forces are always interactions between two objects, however, and you cannot identify a second object for a fictitious force.

F_2 is the force on the outer wall/floor from the inhabitant (ie two objects), and F_1 is the force on the inhabitant from the outer wall/floor, therefore by this definition they are real forces. F_c on the other hand acts on the inhabitant but we cannot identify another object from which the force originates. --FyzixFighter (talk) 00:28, 6 June 2014 (UTC)

Reworded Reaction_(physics) article - the link is okay now

I reworded that "forces come in pairs" torquing of the 3rd law to allow for "rates of change of momentum", and added a citation for it. Now I'm okay with linking to it as long as it doesn't migrate back to that "force-only" wording. Montyv (talk) 00:27, 6 June 2014 (UTC)

Newton's Third Law of Motion: "Another corollary is that all forces in the Universe have corresponding reactions. The only exceptions to this rule are the fictitious fores which arise in non-inertial reference frames. Fictitious forces do not possess reactions." --FyzixFighter (talk) 04:11, 6 June 2014 (UTC)

Something missing

This article fails to make clear that the term 'reactive centrifugal force' in no longer in common use in physics mathematics or engineering and I am not sure that it ever has been. Using the term 'centrifugal force' to mean 'reactive centrifugal force' also not in common use and is extremely confusing.

It has been possible for some editors to find sources using 'reactive centrifugal force' or 'centrifugal force' with the same meaning and although this is sufficient to show that this terminology has been used. In modern (last 40 years or so) teaching and usage the concept of a reactive centrifugal force is deprecated as it is unnecessary and confusing. Not making this clear in this article makes it highly misleading. Martin Hogbin (talk) 16:48, 6 June 2014 (UTC)

The lead has said "The term 'reactive centrifugal force', in relation to the reaction force to a centripetal force, is seldom referred to in modern physics and mechanics" for some time now. And before that for a few years it was even more explicit in linking the article on the modern concept that supplanted this one. So it's not clear what you're saying. Dicklyon (talk) 01:26, 18 June 2014 (UTC)

Direction of force

I removed Dicklyon's references to the direction of the reaction force because it contained no authority in support and is simply a POV. The statement was:

from the point of view of the moon's rotation, it is still a reactive centrifugal force, applied in the direction from the center toward the moon, even though it is centripetal where it is applied to the planet.

The direction of a force in relation to the inertial centre of rotation is given by the acceleration of the body that the force acts on in relation to the inertial centre of rotation: F = ma. If the body is undergoing centripetal acceleration, then the force is centripetal. No one would say that the moon is undergoing centrifugal acceleration. Dicklyon has provided no authority for his statement. He is expressing a point of view that is not contained in any recognized physics authority in violation of the Wikipedia policy on NPOV. AMSask (talk) 17:32, 13 June 2014 (UTC)

There is no disagreement here about the direction of the force. And you are right that nobody would say that that the moon is undergoing centrifugal acceleration. The only point is to say why the force is called centrifugal. Dicklyon (talk) 06:22, 17 June 2014 (UTC)

It is amazing how many books are unable to express this simple concept clearly. Look at these; any good ones? The one that come close is this one, which follows a perfectly sensible explanation by an unexplained "But this concept is quite wrong" (and then proceeds with an even more strained attempt to convert to the pseudoforce concept, which is not in fact in conflict with the concept that they say is "quite wrong"). I suppose they are saying what AMSask is saying: that he doesn't like the fact that the reaction force of the moon on the planet is called a reactive centrifugal force, since it acts centripetally on the planet. Tough--that's what it's called. Dicklyon (talk) 06:45, 17 June 2014 (UTC)

Who, exactly, says that the direction force of the moon on the earth a centrifugal force? Unless you can provide some authority that gives the direction of a force on a body as anything other than the direction of the acceleration produced by that force (ie. the direction of the acceleration of the body on which the force acts), this is just your own personal POV. AMSask (talk) 23:12, 17 June 2014 (UTC)

Like I said, there's no disagreement that the direction of the moon's pull on the planet is toward the moon, which is the same direction as the acceleration, as you say. Do you need a source for that? Is your point of view on that physical fact in any way different from anyone else's? The text you objected to already notes specifically that "the forces on both bodies are centripetal." This is admittedly a special case, relative to the barycenter in a two-body problem. In a system like the Earth's pull on the Sun, the reactive centrifugal force in not generally centripetal, since Jupiter is moving the Sun more the Earth is; that's a case where trying to characterize the gravitational reactive centrifugal force as centripetal just leads to nonsense. Dicklyon (talk) 01:12, 18 June 2014 (UTC)

I added another ref to the Mook page that says, "the sun will feel such a reactive, centrifugal force from each of the planets...". Dicklyon (talk) 01:20, 18 June 2014 (UTC)

Your reference to Mook and Vargish does not support the statement:

"from the point of view of the moon's rotation, it is still known as a reactive centrifugal force,[3] applied in the direction from the planet toward the moon, even though it is centripetal with respect to the barycenter where it is applied to the planet."

In fact the Mook and Vargish reference contradicts the statement that everyone agrees is correct, which is that the reaction force of the planet's centripetal force on the moon is the moon's centripetal force on the planet. What we need is an authority for the statement that there exists a generally accepted convention that a force that provides centripetal acceleration is referred to nevertheless as centrifugal from the point of view of the moon's rotation. While you are at it, please explain what "from the point of view of the moon's rotation" means and why this is not your own POV. AMSask (talk) 13:03, 19 June 2014 (UTC)

Mook does not contradict the fact that in a two-body problem, the reactive centrifugal force of one body on the other via gravity is applied in a centripetal direction on the body that it is applied on. He says nothing at all about that, but instead talks about the more general n-body problem, where the small wobble of the big body that you use to define centripetal is irrelevant since most of the forces are in directions unrelated to it. Only the biggest planet (or the one with biggest gravitational force at its distance) is likely to have its reactive centrifugal force being applied approximately centripetally in the n-body case. This is one good reason why your wanting to call the reactive centrifugal force centripetal is something one seldom sees, and certainly not in situations more general than the 2-body case. Dicklyon (talk) 06:11, 20 June 2014 (UTC)

And the Mook reference does support that assertion that these forces are called reactive centrifugal forces, saying "the sun will feel such a reactive, centrifugal force from each of the planets..." at the end of the paragraph discussing "equal and opposite" forces like the pull of the ball on the string in reaction to the force of the string that keeps a ball going in circles. It's not that complicated. Dicklyon (talk) 06:16, 20 June 2014 (UTC)

The Mook reference says that the reaction force to the centripetal force of the sun on a planet is a centrifugal force on the sun ie. a force pulling the sun outward. But we all seem to agree that the centre of mass of the sun is undergoing centripetal acceleration, ie. toward the centre of rotation (assuming there are only two bodies). [If there are more than two bodies then it is complicated because the com of the sun could be between the centre of rotation and the planet, which I think is the point you were making]. Mook/Vargish do not say that it is centrifugal when it is viewed from the planet's position. They say it is centrifugal in relation to the sun. They make no reference to the location of the centre of rotation. What you need is an authority that says: 'Notwithstanding that all forces and accelerations are centripetal, if you consider the direction of the force not in relation to the body that experiences the force but in relation to the body that causes the force, the direction can be referred to as "centrifugal"'. That is what you are asserting. That is what is being objecting to. AMSask (talk) 20:24, 20 June 2014 (UTC)

But the center of rotation of the Sun is completely not the issue here, nor is the fact that the force on a body moving in a curved path is always centripetal, by definition of f = ma. Even if the Sun were an immovable anchor, it would be pulled on by reactive centrifugal force, that is, a force directed toward the rotating body. The "centrifugal" in the phrase describes the direction relative to the rotating body whose centripetal force we are describing to the reaction force to, that is, the orbiting planet. It has nothing to do with barycenter or wobble of the Sun. Mook says it right, in agreement with other sources that describe this way of looking at things. These are ordinary real forces that we all agree on. It's only the name "reactive centrifugal" that's bothering you, but it has a sensible meaning if you don't twist it into nonsense. Dicklyon (talk) 22:51, 20 June 2014 (UTC)

If Mook/Vargish was attempting to say that the force is centrifugal relative to the planet they would have said that. They didn't.AMSask (talk) 15:00, 21 June 2014 (UTC)

“ ... and follows a circular path, just as the planet does when acted upon by the sun's gravity. But by Newton's third law, if you exert a force on the ball, the ball must exert an equal and opposite force on your hand, and it does. You feel this force as the "tug" of the ball on the string you hold. It is not necessary to posit a centrifugal force. What is sometimes called a "centrifugal force" is a reflection of the force you are exerting on the ball to keep it in a circular path. Similarly, the sun will feel such a reactive, centrifugal force from each of the planets that it holds in an orbit by its force of gravity. ”

Is there any other possible interpretation of what he meant? We all agree on the direction. Mook is just pointing that this reaction force is sometimes called a "centrifugal force". Dicklyon (talk) 15:23, 21 June 2014 (UTC)

It´s only the fictitious centrifugal force in the rotating frame that is involved in the Sun-Earth problem which you are discussing. There is no reactive centrifugal force involved here. Yes, the centripetal force on the Sun (caused by the Earth´s gravity) is part of an action-reaction pair with the the centripetal force on the Earth (caused by the Sun´s gravity), but this is a non-sequitur to this article. In the centrifugal clutch, the centripetal force is a contact force and it does not form an action-reaction pair with itself as between point A on the outer shaft and another point B 180 degrees around the rim of the same shaft. In the centrifugal clutch, the action-reaction pair is the centripetal force exerted inwards by the outer shaft and the reactive centrifugal force exerted outwards by the inner shaft. 83.43.98.14 (talk) 11:54, 8 September 2014 (UTC)

Introduction

I hope that nobody minds that I have removed a section from the introduction. I did so because in the moon planet example given, reactive centrifugal force does not exist. It only exists in contact situations like the centrifugal clutch. In the centrifugal clutch the inner shaft exerts a centrifugal force on the outer shaft while the outer shaft exerts a centripetal force on the inner shaft. In the moon planet example the centripetal force already exists in the form of gravity and not due to an interaction with the centrifugal force. The gravity would remain even if the rotation were to stop. In the clutch, the action reaction pair is centrifugal-centripetal but in the moon planet example there is no reactive centrifugal force and the action reaction pair is centripetal-centripetal. If you think I am wrong then feel free to revert. 95.23.221.174 (talk) 10:04, 6 September 2014 (UTC)

I would also like to remove this sentence from the introduction "A centripetal force is one that causes a body to follow a curved path (rotation)". My reason is that it is best to avoid going into detail about what centripetal force is in an article about centrifugal force. In this article centripetal force should be taken for granted to avoid a debate on whether centripetal force means a force directed towards a center or a force that acts at right angles to the direction of motion. 95.23.221.174 (talk) 10:12, 6 September 2014 (UTC)

the curved path

Noting the recent changes in the introduction, it´s true that a curved path follws from a centripetal force. It´s also true that there will be no reactive centrifugal force without a centripetal force. However, the outward tendency on rotation due to the inertia presupposes the existence of a constraint which would cause a centripetal force and hence a curved path. Therefore, has the curved path not perhaps been introduced prematurely in the introduction? May I suggest that you maybe reverse the order of those two sentences and tweak accordingly? 89.140.133.201 (talk) 20:22, 8 September 2014 (UTC) As in perhaps, ´´´ When a constraint opposes the outward motion, a centripetal force will act inwards on the object causing it to follow a curved path.´´´89.140.133.201 (talk) 20:28, 8 September 2014 (UTC)

Except that the inertia isn't really strictly an outward tendency. It's a tendency to move in a straight line. If the source of the centripetal force is removed, the object doesn't just go radially outward but in a line tangent to the path it was following when the force is removed. For me, it's a more natural progression, similar to the ordering of the laws of motion, to say that the object is not following a straight line as inertia would have it do (1st law), therefore an external force is being applied (2nd law), therefore it is exerting a equal and opposite force on the source of the external force (3rd law). --FyzixFighter (talk) 01:45, 9 September 2014 (UTC)

I was examining the situation from the centrifugal clutch example. The inner shaft expands outwards under rotation. Curved paths and tangents don´t enter into it at this preliminary stage. Only the inertial effect is involved at this stage. The centriptal force comes into the picture only when the inner shaft makes contact with and is constrained by the outer shaft. Once centriptal force and reactive centrifugal force enter the picture, then we will have a curved (circular) path for each of the elements of the inner shaft, but the curved path is only incidental, whereas the causative mechanisms driving the device are rotation and the inertial effect. The tangent that ensues when the centripetal force is removed still involves an outward tendency, and the combined effect of the outward tendency of all elements around the rim of the inner shaft, is for the shaft to expand outwards. What you have written is technically correct, but people had been complaining about the top heavy wording. I could see that much of the top heavy wording centered around the involvement of the unnecessary term ´curved path´ so I attempted to illustrate the effect in question in more simple language using key terms such as inward, outward, center of rotation, constraint etc. As regards the clause about the directions being the same for both the reactive centrifugal force and the associated fictitious centrifugal force in the rotating frame, I was assuming as a matter of course that we were working around the same center of rotation, but I can see now that I should not have made that assumption for the reasons stated in the last paragraph of the inroduction. 141.105.106.140 (talk) 07:42, 9 September 2014 (UTC)

I'm all for simplicity, but not at the cost of being technically incorrect. The idea that inertia is a tendency to move in a straight line tangent to the curve is to me completely orthogonal to the idea that inertia is a tendency to move outward. I also think that it also doesn't work if we ever are dealing with non-circular rotation where the tangent line might correspond to decreasing radial distance. To only describe inertia in terms of the motion along the radius is to implicitly adopt a rotating, non-inertial frame (see EJ Aiton's, "The celestial mechanics of Leibniz in the light of Newtonian criticism" Annals of Science 18 (1):31-41 (2006)). Or, to quote Swetz, "Learn from the Masters!"

The question arises whether the earlier [Leibniz's] concept can be interpreted meaningfully. Considered as an endeavor of the circulating body, or a force acting on the body itself, it does not exist. But if we consider a reference frame fixed in the body and rotating with it, the body will appear to have an endeavor to recede from the centre. This is of course a fictitious force reflecting the acceleration for the reference frame.

I don't think I've ever seen a description of inertia, either in general or in the particular case of rotation), in a reliable source that says that it is an outward tendency of the object. Do you have one? It would certainly clear up this apparent disagreement. --FyzixFighter (talk) 03:04, 10 September 2014 (UTC)

It's true that nobody specifically defines inertia as an outward tendency, but inertia gives rise to straight line motion, which in the examples that we are looking at gives rise to an outward tendency. Put in 'straight line' if you want, it's fine. The important thing is that you don't put in 'curved path' before the constraining centripetal force has been introduced. It's looking OK now apart from the last paragraph in the lead. I think that Mook and Vargish have dreadfully confused the reactive force with the fictitious force. 94.173.45.184 (talk) 20:27, 10 September 2014 (UTC)

Indeed, the "outward tendency" that people speak of only makes sense in a rotating reference frame; let's not conflate those. I took out the "one could" sentence that you didn't like, since it seems to have no direct relation to actual practice or sources. Dicklyon (talk) 20:53, 10 September 2014 (UTC)

action-reaction pair

´´the fictitious force is felt by ALL objects in the rotation frame, unrelated to the action–reaction pair´´. True. But the clause that was removed about acting on opposite bodies was presumed only to apply to cases where the fictitious force IS involved in an action-reaction pair, but best to leave it out now because it was only an unnecessary extra in the introduction. 141.105.106.140 (talk) 08:20, 9 September 2014 (UTC)

What does it mean for a fictitious force to be involved in an action–reaction pair? I thought a fictitious force never had a reaction. If it had a reaction it would be a real force. Or do you have a counter-example in mind? Dicklyon (talk) 20:57, 10 September 2014 (UTC)

Interesting point. I had to think about it. I would say that in cases of actual rotation, the fictitious centrifugal force always forms an action-reaction pair with another fictitious centrifugal force, but that the existence of a fictitious centrifugal force does not mean that an action-reaction pair involving a reactive centrifugal force and a centripetal force also has to exist. But where such an action-reaction pair, as between a reactive centrifugal force and a centripetal force does exist due to the introduction of a constraint, then there will always also be a fictitious centrifugal force involved in the process, observable only in the rotating frame of reference, but whose effects can be felt in any frame of reference. 94.173.45.184 (talk) 12:31, 11 September 2014 (UTC)

No Original Research

I couldn't find any original research in the article. Reference 4 in particular lays out this very simple concept quite clearly. 81.4.183.162 (talk) 09:40, 12 October 2014 (UTC)

reactive centrifugal force

reactive centrifugal force applies to a push or a pull that is directed away from the center of rotation and it only occurs in situations where one body is in physical contact with another body, such as in the examples given in the main body of the article. The planetary example at the end of the lead involves only fictitious centrifugal force. There is no reactive centrifugal force involved in the planetary example. There is an action-reaction pair when considered over the two centripetal forces in the planetary example but these can never be considered to be centrifugally directed and they are not what this article is about. Centri-Fugal means center fleeing. Please don't insert this paragraph again without discussing further on the talk page. 81.4.183.162 (talk) 09:08, 14 October 2014 (UTC)

Looking at the Mook reference, I see that he is talking about a different use of the term 'reactive centrifugal force'. It therefore starts to get very confusing so it's best to deal with Mook's usage as in a section of its own. 81.4.183.162 (talk) 09:24, 14 October 2014 (UTC)

Roche Reference

The Roche reference has been used in this article to argue that the fictitious force is more commonly used than the reactive force. Page 403 in the Roche reference however according to my reading says the complete opposite http://www.marco-learningsystems.com/pages/roche/Motion_in_a_circle_pdf.pdf I'm looking at the part halfway down the first column where it reads,

"This is the centrifugal force of physics, an entirely fictional force [19]. It has now virtually disappeared from school and undergraduate physics textbooks because it can be highly confusing. Indeed, it is not uncommon even for physics authors to confuse the language of inertial and rotating frameworks."

I will remove that sentence in the lead as it appears to be ambiguous. If anybody wishes to restore it, I won't object. 94.173.45.184 (talk) 10:01, 15 November 2014 (UTC)

Just what are you trying to say?

A) Are you trying to say that RCF is any real force that happens to be directed centrifugally?

OR

B) Are you trying to say that RCF is the negative of mass times acceleration of an object in an inertial frame? Meaning, if you will, the physical resistance a mass gives in response to its acceleration through space by unbalanced real forces.

So, which is it? Or is it something else? Every time I read this article I see something different. I added some explanatory text because I was so sure you meant (A), but I read it again and now (B) seems like it fits the scattered explanations better. The article is so strikingly unclear that there's really no way to tell. It's no wonder so many have thought it was quackery. The wordings are so confused and indecipherable that surely it looks like the confused (yet confidently proclaimed) mutterings of a crank.

Somebody please say what RCF is actually supposed to be and we can get to work clarifying it.

72.74.19.224 (talk) 04:25, 1 April 2015 (UTC)

I think it's somewhat something else. Yes, for an object in curvilinear motion, it is "the negative of mass times acceleration of an object in an inertial frame", but only for the part of the acceleration that is orthogonal to the velocity, I think. And that only gives the force vector; it's also relevant to know what that force acts on. For example, if the mass in question is a planet in circular orbit about a star, the force acts on the star (and as some have noted, is a centripetal force on the star even though it's the reactive centrifugal force of the planet; so it certainly can't be A). Dicklyon (talk) 05:20, 1 April 2015 (UTC)

Do you know what I mean by (A)? For a ball-on-massless-string, the string tension points petal and also fugal, The "fugal" part of tension is a "real" force". It's both "fugal" and it's a force (and a real force at that), but quite a different thing from the "centrifugal force" people commonly mean when they say "centrifugal force". By (A) I mean any real force in the system that just happens to be pointed fugally, it's almost trivial actually. I hope the article isn't about (A) because (A)'s notablity would be extremely tenuous, and it would be misleading to imply that (A) is somehow core to and essentially the same as the "centrifugal force" people commonly mean when they say "centrifugal force".

I think it's a good idea to forget gravity for now in this section of the talk page. Gravity's "equivalence" to pseudoforce is a distraction and makes for confusion. In the article(s), gravity and its confusing equivalence issues should be discussed only after explanations are given with examples using the other ("hard") forces (EM, strong, weak). That's just an opinion of mine about communicating on the subject more effectively. I'd like to go with it. :-) 72.74.19.224 (talk) 02:44, 4 April 2015 (UTC)

For more on this, it woud be best to study the sources and see what they're trying to say. Some seem a bit confused, like for a planet in elliptical order, is the gravitational force on the star the reactive centrifugal forces of the planet in orbit? Even though it's not quite in the direction from center of curvature toward planet? Sources seem to differ a bit on this, or are not careful in saying. Dicklyon (talk) 05:23, 1 April 2015 (UTC)

I think that illustrates my point well. If you will, readers shouldn't have to go to confused(!) sources to decipher what an article is about, it should be clear in the text of the article. If some sources are confused (as so many are on this subject), they should be written off as unreliable. If we can't explain what we're saying, and/or there isn't a reliable source out there saying whatever it is we're saying, the article should maybe be deleted for lack of notability?

Whether a "center" is meant to be the point pointed to by the radius of curvature or if it's something else is ultimately a matter of definition, and that is ultimately just a matter of being (again) clear about what's meant when one says "center". As a rule, if there's any way it can be confused as to what's meant by "center" (or anything else), it should be specified explicitly in situ. Though, I can't see how anyone would ever use a definition of "center" as anything other than the point pointed to by the radius of curvature at a given moment. Momentarily curved trajectories of bits of mass are a more general form of the problem, constant circular motion is just a simplification and a steady-state form of that. 72.74.19.224 (talk) 03:08, 4 April 2015 (UTC)