Talk:Mass versus weight

message: * re the billiard balls on the moon. I am a complete layperson but i assume that gravity on earth would increase the friction so the decreased friction on the moon would mean that the balls broke and moved more swiftly, although falling into the pockets more slowly. Any experts there who can answer this question? 89.241.254.21 14:54, 9 November 2007 (UTC)
replies: text: F<=uR is a good approximation for friction (u should be 'mu', the coefficient of friction). In this case, the maximum friction F on a billiard ball would be lower on the moon because the reaction R would be lower, in turn because the weight of the ball would be less. It should be noted that other effects (e.g. lack of drag due to lack of atmosphere) also come into play. In future, Wikipedia:Reference_desk may be able to answer your question. Hope this helps. Sheffield Steeltalkstalk 16:32, 9 November 2007 (UTC)
replies: text: The balls would also be much more inclined to rebound out of the pockets. A “Moon-grade” billiards table would probably have much enlarged pockets to compensate for this. Of course, all of these are subtleties that go far beyond the basic principal being conveyed. And technically, during a break shot, where the racked billiard balls are typically touching each other (or at most a few millimeters away from each other), the opportunity for meaningful differences in friction to come into play as the kinetic energy is distributed is effectively nonexistent (except for the speed of the incoming cue ball). The racked balls’ initial behavior would be very similar to that kinetic demo game where six steel balls hang from strings and “click-clack” back and forth. So, no, they would not ‘break with more swiftness’. Indeed though, they would do better on the Moon at retaining the finite kinetic energy (speed) the farther they got from their racked positions due to less rolling resistance; as Sheffield pointed out, the magnitude of this effect can be calculated. As for air friction, I was imagining the game being played on the Moon indoors in a shirt-sleeve environment (what do astronauts on a Moon base do in their spare time?). Greg L (my talk) 20:25, 9 November 2007 (UTC)

text: oops :-) Serves me right for answering the question in vacuo rather than reading the relevant part of the article and getting the context. Sheffield Steeltalkstalk 20:51, 9 November 2007 (UTC)
thread_title: Billiards on the Moon

message: The See Also section has lots and lots of links, and is therefore a bit cumbersome.  I think it makes sense to keep the links to ones about the concept of mass and weight.  I would keep only Apparent weight, Inertia, Mass and Weight of the current links  Enuja   (talk)03:45, 29 November 2007 (UTC)
replies: text: OK, I trimmed it to what seems like a reasonable compromise. I think everything there now is limited to topics that readers would want pursue for further exploration. Good suggestion. Thanks. Greg L (my talk) 03:57, 29 November 2007 (UTC)
replies: text: How about removing SI base units and SI derived units because SI is in the section?  That's a compromise I'd be happy with.  Enuja  (talk) 04:20, 29 November 2007 (UTC)
replies: text: Short is sweet? OK. Greg L (my talk) 04:25, 29 November 2007 (UTC)
replies: text: I'm happy to see Gravimetry back; the section feels more useful now, even though it's still quite extensive, that's not always a bad thing.  Enuja  (talk) 04:40, 29 November 2007 (UTC)
replies: text: Thanks, but the Converting units of mass to equivalent forces on Earth section has always been there—both back when it was in Kilogram (where it was titled Converting to kilogram-force and newtons) as well as when it was first placed here. All I did was add the graphic later this evening. That makes the subsection stand out, doesn’t it?  Greg L (my talk) 05:08, 29 November 2007 (UTC)
replies: text: I was still talking about links in the see also section.  But, yes, that image is excellent in that section.  Enuja  (talk) 05:40, 29 November 2007 (UTC)
replies: text: Oh, yes. Of course.  Greg L (my talk) 06:21, 29 November 2007 (UTC)
thread_title:  See Also section 

message: While the section on bouyancy is nice, the next paragraph right after claims that a doctor's scale measures actual mass. Presumably it means conventional mass? Or perhaps it's alluding to the fact that the precision is so bad for that scale that it doesn't matter? If so, qualifiers are needed.  Even worse is the next paragraph which claims that lunar scales balances would work the same as on Earth. Yes, if both are in vacuum, but only then. Even if you put them both in atmosphere (say, compare scale-weight on your moon-base), you're not going to measure the same mass-number unless you're weighing two things of equal density, or else you happen to have the density of your atmosphere in your base about 6 times that of Earth-normal (as the ratio of g's), to compensate for the reduced weight-error produced by bouyancy produced on the moon. Achh! More qualifiers needed. But I thought I'd better bring it up here so you can decide what you want to do. I'll add a bit on the problem of measuring unknown masses in air to micro-precision. SBHarris 06:19, 1 February 2008 (UTC)
thread_title:  That nasty bouyancy 

message: According to Einstein's theories of relativity, mass changes with acceleration(e.g., infinite mass at light speed). Also according to the aforementioned theories, gravity is functionally identical to acceleration. Therefore mass should change with a change in gravity. Is there something I'm missing here? Skylerorlando (talk) 01:50, 2 April 2008 (UTC)
replies: text: Yes. Mass changes in relativity according to velocity, not acceleration (they are different things). And you don't get infinite mass at light speed because you can't get to light speed. And even the mass change as you get close to light speed is a function of inertial frame (ie, of the viewer), and so in some sense is not "real" (see mass and mass in special relativity). By "real" I mean it's not something that all observers agree on, and the change it makes in the gravitational field of the object, is mostly to distort it rather than to make it "bigger" (that is, it gets stronger in one direction, but weaker in another, and it can't cause the object to collapse into a black hole). See mass in general relativity. For this reason, most physicists have stopped calling this mass increase a mass increase, and prefer to say that the mass does NOT increase, but the energy and momentum do. The more "real" mass which all observers agree on, in special relativity, is called invariant mass, and it does not change with velocity. SBHarris 05:23, 2 April 2008 (UTC)
thread_title:  Mass, weight, and the effects of gravity 

message: If it is indeed "better", should it not be the first definition mentioned?  (See 3rd para of main article).
David. 161.51.11.2 (talk) 11:13, 17 February 2011 (UTC)
thread_title: A better scientific definition of mass (?) 

message: There seems to be consensus that this article should be deleted.  I am not sure how to do this.  Can somebody advise the procedure? or go ahead and do it?  Timb66 (talk) 22:56, 1 March 2011 (UTC)
replies: text: If you do it, make sure that there's nothing in this article that needs to be rescued. For example, I like the buoyancy section of this article better than I do in the weight article. Of course, you're going to get stuck again, since there really are texts that say that objects held up by buoyancy have less "weight." They'd say that with a balloon but not an airplane, even though there's absolutely no difference is the mechanism by which they don't fall. Both are held up by forces that counteract their weight on a scale underneath them, but in both cases are still transmitted to the ground. As well claim that a wrecking ball has no weight because it's held up by the crane. SBHarris 17:08, 2 March 2011 (UTC)
replies: text: Since it is still here, I vote for it to stay.  As people, even ones who should know, get it mixed up often enough, I believe that there is reason for this page.  This is especially true in countries where pound is a unit of both force and mass.  It isn't so easy to get wrong with kilograms and newtons. The actual physics could go to weight, though, as I noted on the talk page, this is still a research subject. Also, even more recently, related to dark matter. Gah4 (talk) 15:52, 6 May 2017 (UTC)
thread_title:  Delete this article (merge with [[Weight]]) 

message: This is a convoluted way to illustrate the diff. between weight and mass, and seems misleading, but my main concern is that the caption creates the impression that the tension in the chain is a constant equal to the child's weight, which is false. There are other factors involved that muddy the waters, but I can't think of a new caption that would salvage the truth from the confusion this example creates.77Mike77 (talk) 16:57, 5 March 2013 (UTC)
replies: text: The chain does hold all the child's weight (plus weight of the swing seat and chain). The child's weight increases when she accelerates, as in a centrifuge, and varies throughout her arc. The only way to consider that this is NOT true, is to use the moronic gravitational definition of weight propagated as one alternative in the weight article. You know, the one that insists that weightless astronauts on the space station must still have 90% of their weight, because the g field (for resting people) is 90% as strong where they are? In this definition, weight is not something a scale measures, but that you must calculate knowing the absolute value of the g field at some distance in the rest frame of the object producing it. It's an artificial number good for nothing, but some texts support it, mostly because they wrote their definition without considering the contributions to weight that may be made by motion. SBHarris 21:28, 5 March 2013 (UTC)
thread_title:  GIrl on swing caption 

message: The statement Engineers and scientists understand the distinctions between mass, force, and weight is presumably true, but I suspect that some get it wrong, anyway.  This is especially true in the US, where pound is both a unit of mass and force.  Some time ago at an air museum I found an airplane engine thrust specified in pounds, and then converted to kilograms. I suspect that there are many spring scales calibrated in kilograms. Gah4 (talk) 15:27, 6 May 2017 (UTC)
replies: text: Yes, there is "kilogram-weight", which is the gravitational force on a mass of 1 kg. I've never seen a bathroom scale calibrated in newtons. (Technically, they should be calibrated in newtons, but since the mass is proportional to the weight, it makes no practical difference.)77Mike77 (talk) 18:10, 10 November 2018 (UTC)
replies: text: As long as it is in your bathroom, that should be true.  Take it to the moon, and I disagree.  I suspect that the calibration is still close enough at the top of a tall mountain.  Gah4 (talk) 21:26, 31 July 2019 (UTC)

text: See Kilogram-force. The kilogram is a widely (albeit incorrectly) used measure of force in the day-to-day and commercial world. VQuakr (talk) 22:40, 31 July 2019 (UTC)
replies: text: So it is fine for the thrust of a Mig engine, but not the F4 Phantom?  A museum I visit has a comparison of the two, with thrust in pounds and kilograms.  (It doesn't say kg-f.) I asked, and it seems that the Smithsonian has official museum guidelines that say pounds and newtons, but someone goofed. But they still didn't change the sign. Gah4 (talk) 00:07, 1 August 2019 (UTC)
replies: text: Do you have some examples of day to day use?  Not counting spring scales calibrated in kg, with accuracy low enough not to tell the difference. Time variations in g should be small enough, that a scale calibrated in place should be fine. Gah4 (talk) 00:10, 1 August 2019 (UTC)
replies: text: Not quite sure what you are asking here. What improvements to the article are you proposing? Just better (ie, some) sourcing for the section? VQuakr (talk) 00:17, 1 August 2019 (UTC)
thread_title:  ''Engineers and scientists understand the distinctions between mass, force, and weight.'' 

message: What are we supposed to use instead of
"I'm weighing the sample. The sample weighs 50 mg." ?
"I'm massing the sample. The sample masses 50 mg." ?
"I'm determining the mass of the sample." "The sample mass is 50 mg." ?
Darsie42 (talk) 23:20, 27 September 2018 (UTC)
replies: text: Try a dictionary. To mass has a different meaning as a verb: it is like "to gather into a mass"—see, for instance https://www.dictionary.com/browse/mass and more at https://www.onelook.com/?w=mass and if that is not sufficient, try our wp:Reference desk/Language, because it's a bit off-topic here. See wp:TPG. - DVdm (talk) 07:19, 28 September 2018 (UTC)
replies: text: I need the answer to this, as it is now needed in the Mole (unit) article.  There are statements like ... weighs 40.xxxx grams.', which is wrong for this reason.  Gah4 (talk) 21:01, 2 February 2019 (UTC)
thread_title:  verb