Talk:Force/Archive 3

message: IMO the units of measurement section is much too long, and gives disproportionate weight to silliness like the use of kg as a unit of force.--24.52.254.62 00:17, 4 November 2006 (UTC)
thread_title: Units of measurement section

message: As the article stands it says a force causes an object to rotate, and this is not accurate.  No force is needed to keep an object spinning, such as in a gyroscope for instance.  A force is needed to keep an object orbiting however.  Both these motions however are called rotation.  I'm not quite sure how to phrase it to make it accurate.  Any suggestions? Roy Brumback 08:47, 6 November 2006 (UTC)
replies: text: In my opinion, the first sentence of the article should be simple. If you apply a force on a body that is not rotating, it may start rotating. This is what the sentence says, and I think it's good. I would suggest discussing the point mentioned by Roy Brumback later in the article. Yevgeny Kats 15:55, 6 November 2006 (UTC)
thread_title: Rotation

message: I feel, a following statement is not correct:
With the development of quantum electrodynamics in mid 20 century it was realized that "force" is strictly a macroscopic concept which arises from conservation of momentum of interacting elementary particles. Thus currently known fundamental forces are not called forces but "fundamental interactions".
Quantum electrodynamics can talk only about electromagnetic forces. Of course, QFT involved two other interactions later but it did not involved gravity yet (and we don't know if it will ever do it - we don't know if gravitons really exist and how they behave). The best model of gravity we have, is GR. GR does not say anything about exchanging particles, it uses a curved spacetime - a totally different concept. Miraceti 21:19, 12 January 2007 (UTC)
thread_title:  Electrodynamics and force 

message: Is there some reason why there is no discussion of Newton’s three laws here, or did I miss some thing? Carl 22:42, 26 April 2007 (UTC)
thread_title:  Newton’s Three Laws 

message: I just reverted two bits of vandalism. I don't know if it was a one time thing or a couple of classmates chatting over the wiki or something totally different, but protection or semi-protection may be a good idea.
Paulrun 01:07, 10 May 2007 (UTC)
thread_title:  Protection 

message: I went through and made some cosmetic changes to the intro. Among some of the more surprising edits I made:
*I included mass up front. I think this is important since forces only act on massive bodies.
*I removed "interaction" from the definition as this term links to a disambiguation page and is therefore ambiguous as to what is meant by its inclusion. A force is indeed anything that can cause an object to accelerate. That's the only way we can identify the things.
*I included mention of pressure up front. Since we talk about rotations and deformations, not mentioning pressure seemed a bit odd to me. After all, solids and fluids which do not deform respond to the stress tensor by an increase in pressure -- or if you prefer the field approach, forces themselves are defined as that which exists between differences in pressures.
--Nondistinguished 14:54, 19 July 2007 (UTC)
thread_title: Fixing some problems in the intro

message: The section on conservative vs. non-conservative forces was woefully empty. I tried to fill it a bit, but would appreciate help on the matter. --Nondistinguished 15:48, 19 July 2007 (UTC)
thread_title: Conservative vs. non-conservative forces

message: I know the definition of force on this page has been controversial, but, really, it had converged on the "wrong version". I checked a number of standard textbooks to convince myself that I was not out on a limb here: I couldn't find any that were prepared to use Newton's second law as a definition and several had strong statements that this was a Bad Idea. So I have gone ahead and removed the several statements in the article that this is the one and only way to define force, and instead pointed out that force laws were in fact quantitatively defined using static equilibrium well before F=ma was known. PaddyLeahy 23:03, 9 August 2007 (UTC)
thread_title:  Revision of definition section 

message: Note: I find the definition of force given here misleading and, in many contexts, absurd. See my essay “On the Concept of Force”  in part B of my website .
Walter Noll
:(Added to the end of the lead paragraph on the article page at 19:45, 20 August 2007 by special:contributions/70.20.81.44; moved here by me. PaddyLeahy 19:54, 20 August 2007 (UTC)
replies: text: As a matter of fact I agree with Prof. Noll's essay and I hope that if he had got past the lead paragraph he would have seen that the current article is consistent with his viewpoint (which is also fairly standard in modern university physics texts). I'd support a revision of the lead to emphasise the point that F=ma is a poor definition of force. Anyone else want to comment? PaddyLeahy 20:03, 20 August 2007 (UTC)

text: I should have read it properly before writing the above. I like the emphasis on statics, but Noll is actually proposing to found classical mechanics on the twin principles "net force = 0" and "net torque = 0". In each case inertia counts as a "force"; F = −ma for the simple case; hence this is consistent with Newtonian physics. Given that Newton also referred to inertia as a force, Noll's approach plausibly forms an alternative history of how classical mechanics might have developed...he claims it is essentially the way it is taught to engineers. But it is a bit radical for my taste as a physicist to bring back inertia as a real force after all these years. PaddyLeahy 20:23, 20 August 2007 (UTC)

text: I've added the link as a footnote to the point in the text where Noll is mentioned. PaddyLeahy 12:25, 24 August 2007 (UTC)
thread_title:  Dissident view 

message: While mentioned in the text, the mathematical definition of force (F=dP/dt) is never shown in this article.  This seems unfortunate as it seems it should be towards the top of the article.  Can someone that is better with the math markup include this? ThreeE 03:25, 18 September 2007 (UTC)
thread_title:  Missing Definition? 

message: This definatly needs be be more obviously stated in this article:
According to Newton's Second Law of Motion, the formula for finding force is:
F = ma 
where F is the force,
m is the mass of an object,
and a is the acceleration of the object.
-- Penubag  04:15, 12 October 2007 (UTC)
thread_title:  please fix 

message: Since in most modern manuals and essays we use to define 4 kind of fundamental forces I think that the Nuclear forces section can be misleading, I would suggest to create two subsection in the Nuclear Forces paragraph for Weak and Strong interaction, in order to have an overview of all the 4 forces in the article Tatonzolo 08:58, 8 November 2007 (UTC)
replies: text: Fine with me. I just put a stub in. I haven't thought much about the section yet. ScienceApologist 18:04, 8 November 2007 (UTC)
replies: text:  Ok I'll try fo find some words and references to get it done at an elementary level.. Tatonzolo 12:29, 12 November 2007 (UTC)
replies: text: I had a go at it. There is an issue about distinguishing between strong and weak "forces" as technically they are not well-described in the Newtonian model. I am of a mind to keep discussing them together even though they are very different things. YMMV. ScienceApologist (talk) 14:08, 27 November 2007 (UTC)
thread_title:  Nuclear Forces 

message: Finger trouble truncated my summary before it was complete. The word 'massive' is superfluous because all bodies have mass. Because of that including the word might suggest that the everyday meaning of the word, 'of large mass', is meant which could be confusing to the reader. You might argue that a body can be conceived that does not have mass, if so, it will still tend to be accelerated by a force but the acceleration would be unusually large! treesmill 21:45, 14 November 2007 (UTC)
replies: text: All bodies do not have mass. A photon doesn't have mass, for example. The piped link to "mass" should work fine if the reader is confused. We can alternatively say "of any mass". There is also an issue of "tend to cause" objects to accelerate. The only time objects do not accelerate when acted on by a force is when there is another force canceling the effect. If you remove the other force then there will always be an acceleration. ScienceApologist 21:38, 15 November 2007 (UTC)
replies: text: How do you propose to apply a force to a photon? The use of 'mass' as a synonym for body is undesirable and may cause confusion, because the word is commonly used in a different sense in relation to force. I have already disposed of the argument that some bodies do not have mass. I do not understand your objection to 'tend to'. Your wording either means the same thing or is wrong. 'Tends to' says that a force will move a body but leaves room for the possibility that it will be insufficient to move the body, which seems to be what your last sentence is saying, so I can't see how it is an objection to its use. 'Can' on the other hand is misleading since it may be that the force cannot move the body. Unless you can justify yourself I shall reinsert the more accurate version. treesmill (talk) 01:19, 17 November 2007 (UTC)
replies: text: How can a non-zero net force not move a body? Your argument seems to imply that if there is a non-zero net force acting that there is the possibility that it will be insufficient to move the body.PhySusie (talk) 09:18, 22 November 2007 (UTC)
replies: text:  Where has anyone suggested that? The important point is that, as we all know, a body can have no net force acting on it, but when a new force is applied the body may not move. treesmill (talk) 16:53, 22 November 2007 (UTC)
replies: text: The only way a body will not move when a new force is applied to the body is when another force acts simultaneously on that body in which case there is still zero net force acting on the object. ScienceApologist (talk) 15:28, 26 November 2007 (UTC)
replies: text: The point is that the 'other force' to which you refer is a product of the applied force and the circumstances of the body to which it is applied. In such circumstances the situation is precisely as I described it. A force is applied to a body. The force tends to move the body, but may not in fact do so because the body is restrained. Any definition of force that does not account for this common real world situation will only be understood by readers who do not need the explanation. That is not what an encyclopedia is for. treesmill (talk) 00:37, 5 December 2007 (UTC)
thread_title:  Introduction