Talk:Weight

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In law and commerce[edit]

I recently added a few sentences to the beginning of the lede: In everyday English, weight is a synonym for mass. In law and commerce, including product packaging and nutrition labeling, "weight", unless otherwise indicated, means "mass".

This was soon changed to:

In everyday English, weight and mass are functionally equivalent.

In retrospect, I can see that the first sentence was a mistake, since in everyday English weight can be ambiguous. However, changing it to functionally equivalent to mass doesn't seem to be an improvement, since it seems to exclude the actual equivalent of mass as a possible intended meaning.

My main concern here is with how the word is used in law and commerce, including product packaging, nutrition labeling, medicine, the pharmaceutical industry, etc.

What brought me to this topic is my decades-long interest in the history of customary units of measurement, especially English, e.g., troy weights, apothecary measures, centuries-old weights and measures legislation. On the talk pages of many Wikipedia articles relating to these topics, the mass vs. weight argument has come up repeatedly (usually long before I arrived). Much of the confusion seems to stem from attributing the physics definition of "weight" to situations in law and commerce where it does not apply.

Thus, I would like to see some further discussion on this. Thanks.

From NIST Handbook 130 – 2011 http://www.nist.gov/pml/wmd/pubs/upload/10-iva-packlabreg-11-h130-final.pdf

Uniform Packaging and Labeling Regulation - When used in this regulation, the term “weight” means “mass.” (See paragraph I. in Section I., Introduction, of NIST Handbook 130 for an explanation of these terms.)

From NIST SI Unit rules and style conventions checklist http://physics.nist.gov/cuu/Units/checklist.html

When the word "weight" is used, the intended meaning is clear. (In science and technology, weight is a force, for which the SI unit is the newton; in commerce and everyday use, weight is usually a synonym for mass, for which the SI unit is the kilogram.) Zyxwv99 (talk) 14:05, 6 April 2012 (UTC)

This was already near the bottom of the lead, but for clarity & consensus I've changed the lead back (partially), using existing Canada reference. The US reference could be added if desired. Nobody Ent 14:50, 6 April 2012 (UTC)
Thanks. Zyxwv99 (talk) 22:43, 6 April 2012 (UTC)

Does an object in free fall actually have any force on it, "due" to gravity??[edit]

Newton says yes, Einstein says no. Newton would say "g" makes sense for an object in free fall, but Einstein would say that the g field has disappeared in the view (the reference frame) of an object in free fall. Which is why its weight has gone away, and it is weightless. It isn't that it feels to gravitation, rather in Einstein's view, gravitation no longer exists in the frame of an inertial object. So of course weight disappears as well.

The introductory paragraph uses the "gravitational" definition of weight as one possible definition, but it's not clear to me if anybody ever intended that definition to be applied except for objects that are at rest. For objects that are falling or accelerating, clearly some other definition gives forces that better approximate what we feel as weight, and what scales measure as weight.

I believe that the attempt to apply the misguided "gravitational definition" of weight in situations where it was never clearly intended to be applied, is misguided! We could shorten the lede of this article considerably if we moved it down to a "historical" or "special cases" or even "Newtonian" section (which already exists). SBHarris 20:09, 6 April 2012 (UTC)

If (in the Einsteinian view) there's no gravitation why is the group approaching the fall-frame stationary object at an ever increasing velocity?
In any event, I concur the lead was long and estoric and have made a shortening edit. Nobody Ent 23:21, 6 April 2012 (UTC)
You cut out too much, as the operational view (which makes us "weigh" more in accelerating cars, or weightless in the space station) is the "operational view", or the Einsteinian view. In the Newtonian view, only gravity changes weight, and all other things that seem to lessen or increase weight, are false effects.

Newton would say that a rotating centrifuge (or rotating space-stations of science fiction, ala 2001: A Space Odyssey) only produce the appearance of weight. Einstein would say that it's real weight, any time you can weigh something on a scale (which certainly includes in a rotating space station or centrifuge). Newton would say that you feel the "force" of gravity, and in an elevator falling, gravity is still there as a force, but you don't feel it.

Einstein would say that Newton was wrong: you never feel the force of gravity, per se, even standing on the ground-- all you feel is the contact-forces against your feet, that keep you from free fall. For Einstein, the reason you don't feel "weight" in free fall (a falling elevator, vomit comet airplane, or in orbit) is because the push from the floor is gone in all these weightless cases, and you never feel gravity, anyway! So that's really simple. SBHarris 00:26, 7 April 2012 (UTC)(Refactored 15 July 2012)

Is there a reliable source for the above & corresponding edits?Nobody Ent 02:12, 16 July 2012 (UTC)
There are lots of teaching sites on the net [1][2][3] that make this point. And it's sort of obvious, is it not? If the only force that acts on you is gravity (you are in inertial trajectory), you cannot tell that situation from being weightless out in far space where there is no gravity acting on you at all. Thus, you cannot feel gravity-alone, as it feels just like no-gravity. You have to look out the window to see your acceleration relative to far away things, to infer it. But you don't feel it (absent "microgravity" tidal and gradient effects, which are very small unless you're near neutron stars or star-mass black holes). SBHarris 23:15, 16 July 2012 (UTC)

Regarding recent deletion of "in law an commerce"[edit]

A user recently deleted sections of this article dealing with the use of the word weight in law in commerce. To understand my concerns about this issue, see above section "In law an commerce." Also, the picture a spring scale certainly illustrates how the word weight is used in physics and engineering, but the balance scale illustrates the original meaning of the how, and how it is still used in law and commerce. Zyxwv99 (talk) 16:04, 15 July 2012 (UTC)

Per WP:NOTADICTIONARY, different meanings of a term go into different articles. In this case, this article is about the concept of weight as used in science and engineering. The colloquial meaning of the term is dealt with in the article titled mass. To assist readers to find the correct article when an single term has distinct meanings, we use hatnotes and disambiguation pages.TR 16:55, 15 July 2012 (UTC)
In English Law, the pound was described as a "mass or weight". Martinvl (talk) 21:32, 15 July 2012 (UTC)

Pictures of scales[edit]

I like the new picture showing two different scales side by side to illustrate the difference between weight and mass. Now if we can just do something about the picture "Weighing grain, from the Babur-namah" which shows what looks like a mass-measuring scale. Zyxwv99 (talk) 22:32, 20 July 2012 (UTC)

Error/absence of clarity in intro?[edit]

I believe the "engineering version" of weight is the resultant (vertically resolved) force on an object i.e the product of gravity and other forces e.g buoyancy. In this version, an object weighs less in water than in air etc. A helium filled baloon will have negative weight as, though it has (constant) mass, the mass of the air it displaces will be greater than its own. Could the intro be improved to make this clearer? Regarding the weightlessness of freefall, isn't this phenomenom related only to the reference frame? LookingGlass (talk) 03:05, 7 December 2013 (UTC)