Talk:Pound (force)

pound-force

PatrickandBrenda 03:10, 11 August 2007 (UTC) In the United States, which is the primary user of the pound-force, the pound-force is almost universal in its application to industry and throughout daily life. I challenge anyone to reasonably argue

"In most daily contexts in the United States, the term “pound” refers unambiguously to a unit of force. Bathroom scales intrinsically display weight or force. An important note, all scales read force as only a balance such as used in a doctor's office can determine mass. A truck carrying one-thousand pounds of wood refers to the weight or force the wood exerts on the truck. At a local grocery store, one pound of meat will refer to the force or weight of the meat, and may even be weighed using a scale at the meat counter..."

I also challenge people who oppose this to present common everyday uses or pound-mass (other than niche industry uses).

The pound force has historically and continues to be today the primary use of the word "pound." As a Senior Mechanical Engineer for Westinghouse Electric Co. (Other employers include Terex Corp. and Emerson Process Management among others) I have never encounter a company (outside steam power plant designers) that ever (used in the literal sense) use pound-mass.

Very well. Look at a sack of flour in the supermarket. It may say "net weight 5 lb". This amount is given in mass, not only by convention, but legally. If it were other than 5 * 453.59237 g (within tolerances), the seller would be in violation of the law. It would be no defense to say they weighed it at the top of a high mountain, thus its gravitational force was less.

See below and my update to pound mass.

Bathroom scales measure weight by force. It's true. What are they reporting? Mass. Their purpose is to tell you how much mass you have. If you move the scale to various elevations, granted, its accuracy will suffer, because it wasn't designed any better. But notice that alongside the pound amounts are kilograms. Why is that? Because it measures mass.

Incorrect, see below. It reports force, which by definition is the same as pounds mass. But it is of course a force. As you so astutely report, it will also report something different in space. And scale makers have not interest in trying to do something as difficult as reporting mass. Hence, the pound they display is to indicate force. Trying calling a scale maker, request a technical question. They will direct you to an engineer who designs them and decides what it is to display. They will tell it means force. Honestly! 66.41.157.69 02:07, 12 August 2007 (UTC)

"At a local grocery store, one pound of meat will refer to the force or weight of the meat, and may even be weighed using a scale at the meat counter..." - absolutely false. It refers to the mass. The means of measurement is irrelevant - the fact communicated by the statement "your meat weighs two pounds" is: "you have two pounds (mass) of meat". If you try to define something by the method by which it was measured, you quickly run into absurdities. For example, on some spacecraft are devices for measuring the mass of astronauts. They work because when a certain force is applied to the astronaut, the astronaut begins to move, but resists. So, if the method of measuring defines the outcome, what property of the astronaut is being measured? I could take my pick - force, inertia, or mass. Except we don't have to guess. It's mass. Even though the measurement involves force.

This again is incorrect. See below.

Your knowledge of physics in this case is of great concern. If an astronaut is accelerated to create a measurable outcome that would of course be force (f=ma, where the astronaut of some mass is accelerated and therefore the result is force). The mass would have to be calculated secondarily based on what acceleration they used. (Keep in mind he or she would not be on earth so we can not assume 32.2 ft/s^2.) Then to find the derived unit of pounds mass you must use the gravitational constant, as it is required (only) for pounds mass. Where of course g is simply a constant added to compensate for a unit cancellation when this derived unit is used. This is the only way this can be determined. The force applied to the astronaut is of course equal and opposite to the force he or she press against the scale while causing a proportional acceleration. As you can see the force is of course measured on this scale (you can't really mass on a balance in space.) And therefore mass is calculated, not measured. 66.41.157.69 02:07, 12 August 2007 (UTC)

I will try to make the point more clearly. You said above that a scale reports force, and therefore a pound is force. My basis of my rebuttal is that the means of measuring a quantity do not define what is measured, and therefore you're incorrect. Take for example a modern bathroom scale which measures a person's weight via pressure piezoelectric devices. The person's weight (a force) compresses the scale, producing an electric current. The current is processed and the result displayed. If we were to use your method, the user might report that he weighs 190 pounds "of voltage" - clearly an absurd outcome. The solution to this is to realize that the device is communicating a result whose means of measurement is irrelevant. --Yath 03:42, 12 August 2007 (UTC)

All this is not to say that the pound isn't a unit of force. It is. But it depends on context. I've shown you some contexts where it's a unit of mass; there are many others where it's a unit of force. The points are: 1) it's more often a unit of mass. 2) writers of encyclopedias don't get to choose which use is more important. We just observe and report. And if we don't like the way people use terms, tough. --Yath 06:02, 11 August 2007 (UTC)

Wrong an encyclopedia is not to follow the crowd, but to report the truth even if you don't like it. See my contributions on pound mass for problems with your arguments.

Unfortunately, "In this you are completely wrong Yath. While 5 lb of flour in a grocery store, by defintion is both 5 pounds force as well as 5 pounds mass. The use referred to is force. The "legal" basis that you refer to I would like you to quote specifically from law text. The use of pounds force in no way is illegal, as the difference in weight between the bottom of the sea and the top of Everest is inconsequential. I have worked for and with mass manufacturers of materials such as Cargill and Campbell's and I can tell you unequivocally the unit used is force. And to my knowledge they have never been (or at least never successfully) sued for using force. Like all others they use scales (I can't emphasis this enough), which can only determine force. They are never specially calibrated for elevation. They are calibrated at a NIST qualified facility and then sent back to the facility for use."

Again what technical basis is your knowledge based on? Do you work for NIST, a professor, any number of other expert positions on this topic? 66.41.157.69 02:07, 12 August 2007 (UTC)

No, none. P.S. - it will be easier to follow this conversation if you sign each of your paragraphs.

I suppose the weighing-things-on-a-mountain example was a poor one, because we've gotten caught up on the inconsequentiality of the difference in gravity while that really wasn't the point. You're right, it is unlikely for anyone to be sued, because the difference in measurement would be beneath the tolerances. At any rate, to quote U.S. law that is relevant:

Commercial units of weight and measure in common use are based on the yard and the avoirdupois pound.[...]1 pound (avoirdupois)=0.453 592 37 kilogram US CODE Title 15,205

This demonstrates that items sold "by the pound" are sold by mass. It's further reinforced by the inclusion of SI units on packaging. --Yath 03:42, 12 August 2007 (UTC)

Well, I think you are still wrong on the scale. :) Voltage is directly proportional to force, and it is calibrated as such, by applying a known force. Scales will always only measure force. Although people may equate it to whatever they please. As for commerce, I stand corrected! I wouldn't have believed it until I read in law. Indeed, in 1993 NIST changed their definition of "weight" (in reference to commerce anyway) to mean "mass". I added a section to the pound-mass article to describe my references and research. I would have expected more from NIST than to bow to Politicians, but so it go. Can't bit the hand that feeds you.PatrickandBrenda 18:28, 13 August 2007 (UTC)

Careful here. The archetypal scales are pan balances. Pan balances do not measure force, they compare masses; and do not require adjustment for local g-force, so they do not measure forces. The earliest definition of the pound was in London for use with pan balances. So the pound was first and foremost a measure of mass. And the fact that this is so matters with very precious materials- the g varies over the surface of the earth, and the weight varies and spring balances need adjustment to correct the variation of weight to give an accurate measure of the mass of these products.WolfKeeper 18:50, 13 August 2007 (UTC)

I'm a little out of my league on this topic, but I believe scale actually comes from scalepan. The pan used on those ancient balances. So, I'm not sure scale would have been the proper term even then. Scale is also a word for bowl or cup. I could image that is how a single plate you put something on became known as a scale. Either way, for a long period people did not differentiate between mass and force, because they did not know the difference.PatrickandBrenda 21:51, 13 August 2007 (UTC)

I think that the concept of force didn't even appear until Newton, about 3 centuries later, so yeah. And without a concept of force, the original concept was much closer to mass than weight, since weight is a force.WolfKeeper 21:59, 13 August 2007 (UTC)

I think "scale" probably suffers the same issues as pound (most assuredly on the same timeline), and is best considered after the differentiation became clear and accepted. =) But I believe correct use of scale is to weigh, which implies force and to mass to find mass. (such as in mass balance or to mass a lead slug) It is often misused in SI countries, but in my opinion that's to be expected when someone goes from weighing 200 lb(f) to being told they are 91 kg, a by product or switching from a force-based system to mass-based. One just assumes to same usage of having been "weighed". And vice versa for someone having gone from a regular bathroom scale to a balance at a doctors office. Dr. after all studied biology and probably carry little about physics or whether they are weighing or massing. Just my thoughts there. PatrickandBrenda 21:51, 13 August 2007 (UTC)

Actually no, to my recollection prevailing thought before Newton and his concept of gravitation had nothing to do with mass as you are viewing it. And it could be at least as easily asserted it actually was closer to force than mass. To the point, prevailing theory of the time was that everything was comprised of "elements"; namely earth, water, fire, and wind (or air). Each could be determined by its naturally tendency to rise above the previous. Wood for example, although substantially earth, floated; and this made sense by the theory because wood contained a lot of fire, which was lighter than water. As was evidenced by burning it. Their experience was of a person living in a physical world dominated by gravity and force, not abstract. An ox could plow by pulling hard against a yoke. And enough wood lets you float stone down a river. Too much stone crushed a cart under its weight. This is why many historically systems are force-based. Their weights of course had mass. It's not possible to have been massless. But force is how we sense the physically world. We can't sense (in the literal sense) mass, we can only feel the force it creates. PatrickandBrenda 02:29, 14 August 2007 (UTC)

pound vs. slug

Will you guys stop this edit warring and find a cite to settle the matter? edit, revert... It's not like this is a matter of opinion or anything. --Yath 07:41, 19 August 2007 (UTC)