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Reviewing Cheatsheet[edit]

The following highlights current issues. Feel free to either add the issues you've identified, or to strike them as they've been resolved.

WikiProject Physics' Reviewing Cheatsheet 06:44, 15 July 2008 (UTC)

Do not remove the elements, but rather strike them as they becomes useless or irrelevant (i.e write <s>text to be struck</s>) to indicate that this element was verified and found to be alright.
If everything in one of the section (i.e everything in one hidden-box has been addressed), change the color of the section from "red" to "green".
This cheatsheet can be used by anyone.
To add the Reviewing Cheatsheet to an article's talk page, simply place {{subst:Wikipedia:WikiProject Physics/Quality Control/Reviewing Cheatsheet}} immediately before the first section.

Cheatsheet last updated by: (signature)


Speed is the essence of things. Such a common expression.

It all started with my having to help my daughter write an article on "Slow down, you are moving too fast". I have read a book by an American Author called James Gleick - not sure if I got the name correct. He wrote a book called Speed. He is also the author of a book called "Chaos". I am looking for this book. Wonder if anyone can let me know the correct name of the author.

How comes speed and acceleration have no direction _ They are vectors and definitely they have directions.

If you want to know anything about motin or otherwise just speak to a West Bromwich Fan

Speed isn't a vector, it's scalar. Velocity is a vector (speed+direction). And acceleration has direction only indirectly.. you can accelerate by either speeding up (forwards) or slowing down (backwards), though which direction you are moving doesn't matter, you're either slowing up or you're slowing down. And who on Earth is West Bromwich... >_< Dan 00:08, 14 January 2006 (UTC)

hey can someone tell me the difference of speed and velocity >.< —Preceding unsigned comment added by (talk) 10:45, 2 December 2010 (UTC)

list of common speed[edit]

I think it is useful to have a list of speed for common moving objects. Please join me if you agree. --Leo 14:59, 20 April 2006 (UTC)

Yep... Speed is scalar... So Velocity is more accurate to use... No one runs backwards as fast as they run forwards... So it must be treated accordingly

Average Jogging Speed or World Class Marathoner?[edit]

A world class time for a marathon is less than 2.5 hours. That translates into about 16.8 km/hr or 10.5 miles /hr. While it would be wonderful if we all jogged at 10 miles / hr and could dream of hitting record paces if we trained a few extra hours everyday, these atheletes are slightly out of the league of the "average long distance jogger".

dont believe anything i just edited this and no one even knows if any of this is true

I agree. As an avid runner myself who enjoys running 10k or so every other day, I never get those kinds of speeds. I have a GPS watch which tells me my speed, and If im feeling good, I can keep up 13km/h for 30 minutes. Then I come here and read the average speed is 16kph for long distance. Theres no way that can be accurate. I can see it being possible for the professional marathon runners, but I myself, am already considered above average I think. I would say an average run speed, based on my observations of other people, is around 9km per hour.007craft 16:31, 14 June 2006 (UTC)

I would say 5-6 mi/h or about 8-10 km/h could be considered reasonably "average" for a long distance runner. For a concrete example, the median finishing time for the last New York marathon was about 4:39, which corresponds to a speed of 5.6 mi/h. Itub 16:11, 19 June 2006 (UTC)


I'm sorry if this isn't the place, but has a page for "instantaneous speed" been created? Or is there a page from which I can aquire information on it? If not that might be a nice addition to this page as well.

het where is the speed and the egg color and the Icubation

                    help kendra

          Can you give an example of what you would like to see on here?  what do you mean by instantaneous speed?  do you have any

reliable sources? ~ORANGE~ 22:25, 28 March 2009 (UTC) —Preceding unsigned comment added by Rcnaranja (talkcontribs)

4 times energy for doubled speed[edit]

I have a question,

Why when you double the velocity of an object, you quadruple its speed rather than doubling it?

Has it anything to do with E=mc2 wherein mass is converted into energy by the square of light?

I mean if you "put" kinetic energy into an object, will part of it become "potential mass" and the rest actually become kinetic energy? Is that what explains why you have to square the number of times you want to increment the velocity in order to know the energy/power required?

I've looked everywhere and no one seems to explain why you have to square the energy in order to increment the velocity

I think you are a bit confused. When you double the velocity, you do double the speed in the direction traveled. All speed is, is the magnitude of the velocity. Therefore both forward 3 m/s and backwards 3 m/s have the velocities +3 m/s and -3 m/s, respectively. They have the same speed, 3. What gets quadrupled is the kinetic energy. KE = (1/2)mv^2 where m is mass and v is velocity. If we plug in 2v for v (i.e. doubling velocity), we get the new kinetic energy (1/2)m(2v)^2 = (1/2)(m)(2^2)v^2 = 2mv^2. We see this is quadrupled since 4*(1/2)mv^2 = 2mv^2. As for the other part of the question about the role of E=mc^2. This equation comes from special relativity and tells us how much energy an object would have if all mass could be converted to energy. This formula is only useful with other energy equations when an object is moving at a substantial fraction (at least 10%) the speed of light and thus is not relevant to everyday calculations of velocity, speed, momentum, or energy.Aohara1986 06:42, 19 October 2007 (UTC)


The article should use a consistent notation for speed; actually it´s difficult to read because of different symbols and the use of |v|. I think it could use v for velocity and v (in normal text) for speed, which is common notation for vectors and scalars. --Canaima 01:14, 19 October 2007 (UTC)


This article seems confusing on some accounts, and out right wrong on others. First of all, it defines speed as distance over time, but this is incorrect. Speed is the magnitude of instantaneous velocity. Secondly, it then goes on to discuss instantaneous speed in the portion of the article label "average speed". —Preceding unsigned comment added by (talk) 13:41, 4 September 2008 (UTC)

Thank you for your suggestion. When you feel an article needs improvement, please feel free to make those changes. Wikipedia is a wiki, so anyone can edit almost any article by simply following the edit this page link at the top. The Wikipedia community encourages you to be bold in updating pages. Don't worry too much about making honest mistakes — they're likely to be found and corrected quickly. If you're not sure how editing works, check out how to edit a page, or use the sandbox to try out your editing skills. New contributors are always welcome. You don't even need to log in (although there are many reasons why you might want to). --Closedmouth (talk) 13:58, 4 September 2008 (UTC)
I've made some changes to the article that hopefully make it less confusing (and not at all wrong!) I've commented out the discussion of average speed, harmonic means and so on - not really a reflection on whether it was right or wrong, just that it seemed far too much detail for something that feels more like an introductory article. If it's felt to be important, I would suggest putting it in a separate article with a link from this one. Djr32 (talk) 18:59, 14 December 2008 (UTC)


i have to do my science project and this is confuzing! —Preceding unsigned comment added by (talk) 11:26, 9 May 2009 (UTC)

Curious question[edit]

What is the fastest observed astronomical object? Albmont (talk) 17:28, 26 May 2009 (UTC)

Speed is the rapidity of movement . ` ccatorzeh .. —Preceding unsigned comment added by (talk) 12:02, 9 September 2009 (UTC)

Merger proposal[edit]

There is a discussion taking place on the talk page of Classical mechanics about revamping the structure of the Classical mechanics articles. Included in this discussion are ideas about merging groups of articles under a broad heading for each group. There are some good reasons for doing this. For instance, this article, Speed, would be one section in an article with a broader heading such as Motion (in classical mechanics). Other sections would be merged articles such as Velocity, Displacement vector, and Acceleration, with one or two more. These are all relatively small articles anyway, but that is not one of the reasons for the merge idea. It won't happen for awhile. Perhaps the editors here would like to weigh in on this discussion. It is located here.

Length of path (s) cannot be substituted by "distance"[edit]

I fail to see why the "length of path" (usually denoted by "s") is sometimes avoided or inapropriately substituted by "distance" or "displacement" in this article and elsewhere (e.g. in the article on work). If the statement "The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval" were true, then the average speed on a full circle would always be zero (zero displacement or distance between the initial and final point). —Preceding unsigned comment added by (talk) 00:58, 17 July 2010 (UTC)

"Distance travelled" means something different to "distance between start and end". The first means path length, the second is a displacement. -- Dr Greg  talk  01:26, 17 July 2010 (UTC)

Apologies: you are right. I was mislead by the link to the word "distance" alone (although, if one reads through the linked article far enough it is OK) —Preceding unsigned comment added by (talk) 02:22, 17 July 2010 (UTC)

Gonzales unit[edit]

Most of the derived SI units have been given eponymous names: Coulomb, Farad, Tesla and Watt are a few examples.

The only named unit of speed is the knot, which is not an SI unit. Defined as one nautical mile per hour, it is also imprecise, since the exact length of the nautical mile has varied over time and from one authority to another.

The SI unit of speed (actually velocity) is the metre per second, symbol: m·s-1. I propose that it should be given the name of Gonzales (symbol: Gz) after the eponymous "Speedy". The approved CGPM prefixes would apply very conveniently: a milli-Gonzales (mGz) would be appropriate for expressing things that move at a snail's pace, and the speed of light in a vacuum would be 299.792458 mega-Gonzales (MGz). I further propose that the micro-Gonzales (µGz) be treated as a special unit. It would be a dimensionless virtual unit, reserved for expressing the speed at which committees move towards a final decision.

martinev (talk) 13:14, 12 October 2010 (UTC)

Try asking the BIPM to do that, or even try to popularize this unit yourself. Anyway, article talk pages on Wikipedia are for discussing improvement to the associated article. A. di M. (talk) 18:47, 12 October 2010 (UTC)

Speed and velocity[edit]

The article on speed is nice little article, with neat mathematical presentation. Still, it could be somewhat improved, particularly with respect to constant and average speed. Also, the use of the expression "distance travelled" (especially when without "travelled") may be misleading, the "length of the path travelled" would be better. But the main problem is that speed is explained (particularly in the lead) using a more complex notion of velocity.

This should be avoided in the lead, or the two articles should be merged. The velocity article is a mess anyway, and it should be written anew. The only issue is whether speed should be kept as a separate article. Any suggestions?--Ilevanat (talk) 00:41, 16 December 2011 (UTC)

(apparently not) --Mr. Guye (talk) 20:57, 19 April 2014 (UTC)


The usage and primary topic of slowness is under discussion, see Talk:Slowness (novel) -- (talk) 22:54, 1 December 2015 (UTC)


User DVdm has reverted some of the text I have added to this article: "Mathematically speaking, it should be noted that, for example, an object may pass another even though they have the same velocity at the instant, if one has a greater acceleration. For a discussion of this, see Marsden & Weinstein Calculus Unlimited, a free and legal on-line copy is available at".

I was going to change it for: "Mathematically speaking, it should be noted that an object may pass another even though they have the same velocity at the instant, if one has a greater acceleration (for example). For a discussion of this, see Marsden & Weinstein Calculus Unlimited, a free and legal on-line copy is available at".

For some context, please note that it was on the section added by me, "Psychology". I think it's helpful, as the laymen may think differently from that. And it's important to note things that may be interpreted in wrong ways, and we should make words of caution, so that they don't be.

Following the tradition of Henri Poincaré, I decided to talk more about intuition on this article. Mathematics has many aspects, it's an art, but not only that, it also involves computation, observation, etc... It's an art, a science, and intuition is very important IMHO.

I would like to know the opinions of other editors on this matter. I would like to have the text reinserted.

Sincerely, MathKeduor7 (talk) 17:56, 6 May 2016 (UTC)

Yes, I removed it for the given reason. The wording was also not encyclopedic—see wp:NOTED.
As we are talking about this now, I tried to verify the source that you used for the remainder of the section ([1]). Google books ([2]) does not provide page access, so I can't verify. My question: does Piaget indeed state in this book that this same idea was considered by many others before Piaget? - DVdm (talk) 19:03, 6 May 2016 (UTC)
Thank you very much for your kind answer, DVdm. In fact, it's very bad when there is no preview on Google Books, and it makes very hard to check the references. I wrote it by memory, I will check, but if I remember right he mentioned Einstein as one that thought of it before, so there is at least one "other". He also cited an article of his own about this, it's in French, but maybe there are more references there. It's just a popular book, not very serious, but by an authority in psychology. I commit myself to see if it mentions many others that considered it before. If I don't find a reference I will change it, even though I find it very plausible information. Thank you again. MathKeduor7 (talk) 19:19, 6 May 2016 (UTC)
Okay... I was unable to access Piaget's original article, it was even translated into English, but it's behind a pay-wall it seems. It seems that Einstein was Piaget's inspiration to study it, but the first to make a real systematical study was Piaget himself. Everyone cites him (many, many, many times) on this matter! :) I will make a change there. Thank you for your diligence. I am still learning the rules and guidelines of Wikipedia. Also, My English is not very good (I am not a native speaker, you know), making things more difficult. MathKeduor7 (talk) 19:46, 6 May 2016 (UTC)
It looks good now. :) I am upset that the other part was removed, but I understand your reasons. Have a good day. MathKeduor7 (talk) 19:57, 6 May 2016 (UTC)

Piaget devised experiments to investigate it (instead of merely hypothesizing and speculating about it like some others were doing at the previous century), and this was indeed a huge step towards the dissemination of empirical discoveries and justifications to the many claims and hypothesis made in the field of psychology. If we consider this, it is not so much surprising that he was more influenced by physicists than from people of other fields after all. —T.M. — Preceding unsigned comment added by TarotMagen (talkcontribs) 12:10, 26 July 2016 (UTC)

Wow, the section I have started, which was originally in a pretty bad state, was improved a lot since then! Thanks a lot to the editors. This is one of the nicest things about Wikipedia! By the way, it's very hard to write about psychology, because the notions are not so well-defined like in mathematics and in some other fields. It's always hard to attribute priority, with that phrase with "many others" I was trying to convey that Piaget was not claiming full originality in his idea, as he made that clear, and it could serve for interested reader to dig more about the subject. Another thing: maybe there is another problem there in the section, the excerpt "the intuition" could be problematic, because there is not only one intuition about speed... Indeed it varies with personal development and different people. But I won't try to improve it, as I could make a mess, and I'm retired and very tired to come back. MathKeduor7 (talk) 15:12, 10 December 2016 (UTC)

Citations are needed[edit]

Most of the article's current text is unsourced, making it difficult or impossible to check the claims and expand the article. It is better to avoid popular physics books for laypeople, except for the more introductory passages. Always give preference, whenever possible, to peer-reviewed, rigorous and formal, scrutinized academic studies on physics, which require more background on mathematics and physics to be understood but provide much more guidance on where to find more information about the uses and limitations of this concept. --A concerned user: Hayohamm (talk) 05:35, 20 July 2016 (UTC)