Talk:Apparent weight

This article was nominated for deletion on 24 November 2011. The result of the discussion was keep.

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Archive 1

Merger proposal[edit]

This article (Apparent weight) has recently survived a deletion proposal (not instigated by me), but I believe a proposal to merge the content to Weight should now be considered separately. I believe the original premise of this article was primarily that a body's "weight" was unaffected by its acceleration (e.g. in an elevator, in free-fall), whereas its "apparent weight" was affected. However, this premise seems to have been invalidated by the fact that "weight" itself, in one of its definitions, is the acceleration-adjusted weight (e.g. increases and decreases in an elevator). There are other quibbles surrounding buoyancy and other incidental factors which I will not go into here (and on which I do not believe the articles are presently completely coherent and consistent), but I do not believe these justify a separate article, especially given that they must anyway be mentioned at "weight". Fundamentally, my point is that "apparent weight" is not a separate concept but is merely one particular way of measuring "weight". 86.167.19.90 (talk) 02:33, 15 December 2011 (UTC)[reply]

I certainly would support that. I'll note that the article currently has no sources -- while there are references, they are not to sources discussing apparent weight Nobody Ent (Gerardw) 02:43, 15 December 2011 (UTC)[reply]
I support a merger also. S B H arris 05:06, 15 December 2011 (UTC)[reply]

I don't know how to phrase this without being accused of WP:POINTy, but... If we remove all unsourced material from the article ... there's nothing left to do but create the redirect to Weight#apparent weight, right? — Preceding unsigned comment added by Nobody Ent (talk • contribs) 11:44, 15 December 2011 (UTC)[reply]

We shouldn't merge the contents here to the Weight article. The Weight article is a prominent article that gives the basic definitions. That article should be of high encyclopedic quality. This article can give detailed examples that are useful to certain wiki readers who want to see such examples. Everything here is trivial primary school level physics, so there is no requirement to source anything here at all; citing one basic physics textbook would be more than enough. Count Iblis (talk) 15:01, 15 December 2011 (UTC)[reply]

One of the five pillars of Wikipedia WP:NPOV, clearly states "This policy is non-negotiable and all editors and articles must follow it." . Why not move the article to Wikibooks and add a link from the weight article? — Preceding unsigned comment added by Nobody Ent (talk • contribs) 19:58, 15 December 2011 (UTC)[reply]

Oppose merge There's plenty of sources that discuss apparent weight, see below.

Apparent weight is really rather fundamental. I only ever took one physics class and I remember it being covered. Silver seren^C 20:08, 22 December 2011 (UTC)[reply]

It's perfectly fine if you want to write the article. But as it stands now it does not begin to meet verifiability. I'm going to redirect again ... why do you sandbox something and the replace the redirect when you're done? Nobody Ent (Gerardw) 20:16, 22 December 2011 (UTC)[reply]

Um, no, why don't you stub it and add one or two of the sources I linked and it can be worked on from there? I'm not going to sandbox something that the people supporting a merger didn't bother to look for easily available sources. :/ Silver seren^C 21:05, 22 December 2011 (UTC)[reply]

The existing content at Weight is pretty much the same as a stub, right? I don't want to be discouraging, but I think what you'll find when you dig into it is that "apparent weight" is a house cards ... it's not real physics thing, is a loose description textbook and magazine writers like to throw around. I doubt you would find a published academic paper on "apparent weight." Nobody Ent (Gerardw) 21:09, 22 December 2011 (UTC)[reply]

Au contraire, there are a number of academic papers that heavily involve apparent weight. What's interesting is that there are, indeed, different versions of it. There is the physics version (which is in itself also broken down into a more macro scale and also apparent weight of particles) and there is a psychology version based on senses and motor neurons. But, here you go:

A stationary apparent weight shift from a transient Machian mass fluctuation

How important are changes in body weight for mass perception?

Weight versus gravitational force: Historical and educational perspectives - This one sounds interesting

Charpentier (1891) on the size—weight illusion

Slurry characterization by hydrostatic pressure measurement — analysis based on apparent weight flux ratio

Using apparent molecular weight from SEC in controlled/living polymerization and kinetics of polymerization - Particles again

Apparent Weight of Photons - There seems to be a lot on particles

APPARENT-WEIGHT MEASUREMENTS OF ROCKET PAYLOAD AND TEST STRUCTURES - Interesting...I suppose these could be used as examples.

Apparent weight changes in an elevator Here's a pretty basic explanation of it, good for the layman definition, I would expect.

So, there you go. A lot more where that came from. I'm not sure if this is meant to be an overall definition of apparent weight (which would include the psychology stuff) or just apparent weight in physics (which would be the macro and particle stuff) or we could even split up the two physics types if we get enough information. From the looks of it, this is meant to be just covering the macro physics stuff, but we may want to broaden that a bit. Silver seren^C 21:41, 22 December 2011 (UTC)[reply]

The sources above are basically all crappy sources. For example, [Apparent weight changes in an elevator] was written by a physics teacher at Baldwin High School. If he thinks that weight changes in an elevator are "apparent weight" and not "real weight," or simple "weight" (as ISO defines it) then that is his problem. If the elevator cable snaps and the Otis brakes down't work, I guess this guy thinks that the falling elevator passengers are only apparently weightless, and not really-actually-truly weightless. Dr. Einstein would beg to disagree. Again, however, I see no reason why Wikipedia has to follow the prejudices of some high school teacher in Pennsylvania rather than the basics of modern physics.

There may be some justification in an "apparent weight" definition as being "what the limited-area spring-scale sees," since scales cannot cover the entire surface of the planet, and thus some of the weight that is removed from objects by buoyancy or aerodynamic lift, or other simple suspension devices (like a cable pulling upward from a sky crane), doesn't know up on the scale that is directly beneath the object. Instead, this weight is transferred to other parts of the planetary surface, like to the feet of a crane, where scales there would measure it, if they existed. So weight really is always what spring scales read, with the caveat that sometimes the available scales can't cover the entire distributed load, so they can read incorrectly in cases of weight-reduction through bouyancy, or mechanical lift. But if you have enough scales to read the transferred force, it always shows up somewhere. The sum of it, is the weight. S B H arris 01:16, 10 January 2012 (UTC)[reply]

Identical to "weight"?[edit]

I see that "apparent weight" is now the "force the body exerts on whatever it rests on". Does everyone agree that this is identical to the second definition of Weight, which is "the force an object exerts on a scale, and is equal to the force required to support it"? 81.159.109.119 (talk) 13:00, 24 December 2011 (UTC)[reply]

It's not the same. Weight is the force a body exerts due to gravity. Apparent weight is the changed force that a body exerts when an upward or downward force affects a body. It is extremely important in various fields of study, including fluid mechanics and the physics of space (near weightlessness). Silver seren^C 19:11, 24 December 2011 (UTC)[reply]

The definition of weight that I quoted from the article Weight also varies when an upward or downward force affects the body. The article explains as much. It also explains that "This force measured by force-scales is the same as what some other sources term the object's 'apparent weight'". I ask again, what, if anything, is the difference? Give a specific instance when "force the body exerts on whatever it rests on" is not the same as "the force required to support it".

81.159.109.119 (talk) 20:23, 24 December 2011 (UTC)[reply]

When the body is undergoing acceleration. e.g. in elevator accelerating downward. Nobody Ent (Gerardw) 20:55, 24 December 2011 (UTC)[reply]

The force required to support it (by the elevator) is still the same as the force it exerts (on the elevator). 86.181.174.116 (talk) 03:01, 29 April 2012 (UTC) (BTW, I was 81.159.109.119; sorry for the incredibly long delay, but I forgot all about this thread, and only just stumbled upon it again recently!)[reply]

But the elevator isn't supporting the body -- it's only partially supporting it. Nobody Ent 22:02, 29 April 2012 (UTC)[reply]

[Sorry, I have deleted my attempted replies because I have really lost track of the argument after all this time.] 86.160.223.137 (talk) 23:14, 3 May 2012 (UTC)[reply]

The force required to support it is something completely different. The name for that is the normal force. Silver seren^C 21:13, 24 December 2011 (UTC)[reply]

I think the second Weight definition is in the context of how the weight quantity is measured. Apparent weight is ... well, it depends. Which is why I haven't been a fan of this article. Nobody Ent (Gerardw) 20:55, 24 December 2011 (UTC)[reply]

It would probably be better to focus on the particle aspects of apparent weight (and potentially near weightlessness), as those are the parts of it that are wholly different from everything else. Silver seren^C 21:13, 24 December 2011 (UTC)[reply]

"Apparent weight" as "force the body exerts on whatever it rests on" is the same as the second definition of Weight, which is "the force an object exerts on a scale," but that is subtly different from "the force required to support it." The reason (as noted at the end of the section above) is that the force required to support an object may not all be supplied by the scale it is sitting on. The force supplied by the scale is (by Newton's third law) of course the same as the force the object exerts on what it rests on-- but the missing forces of lift, buoyancy, and suspention, are all missed by a small scale just under the object. Instead, they are transferred to other areas of the supporting planetary surface where there may not BE scales to measure that weight. If there were scales all over the planet's surface, the missing transferred weight would be seen, and total scale-weight would be THE weight. Instead, a small scale may miss transferred weight (as in bouyancy and aerodyamic lift) and so the fraction of the weight that a small scale shows when there are lifting forces on the object weighed, can be thought of as "apparent weight". Thus, apparent weight is not the same as weight, due to transfer effects and scale size; otherwise, they would be the same.

As I said in TALK:weight, an airliner exerts the exact same force on the surface of the Earth, whether sitting on a runway, or in flight (neglecting gravity-height variation). The difference is merely in how much the weight is spread out on the land, when the plane is flying.

The same is true of a balloon before it is inflated, vs. after it is filled with hot air and floats. If a folded balloon weighs 1000 kg when sitting on scales, the atmosphere of the earth weighs 1000 kg more after the balloon is inflated and in flight, even if scales right under the balloon now read zero. The only problem after balloon take-off is the same as after airplane take off: there aren't enough scales spread out over the land to measure the slight increase in pressure caused by the balloon or the airplane. However, if there were, we'd see all of its weight.

Fundamentally, the problem is no different than having a man stand on a bathroom scale at the bottom of a wading pool. He'll weigh less due to bouyancy as measured by this one scale, but if the pool were sitting on the surface of a far-larger giant scale, his full weight would show up, no matter what he did-- even if he laid down and floated on the surface. That is where apparent weight is different from weight. S B H arris 01:33, 10 January 2012 (UTC)[reply]