Talk:Force/Archive 3

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Units of measurement section

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)

Rotation

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)

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)

I agree it should be simple, but not at the expense of accuracy. As it's written, it makes it sound like a force it necessary to keep it rotating, which is not true in the case of spin. Roy Brumback 00:36, 7 November 2006 (UTC)

I've made a stab. I think the key is to emphasise the difference between a point particle and an extended body. A point particle doesn't rotate. The points in the gyroscope keep spinning because of the centrepetal force being provided by the structure of the metal. A gyroscope needs forces to keep spinning, they are just internal stresses. A "see also" bit pointing to moment would be good too.Rpf 14:11, 8 November 2006 (UTC)

This must be one of the hardest articles in Wikipedia to write. There are two issues; firstly it is meaningless to talk of motion without indicating what datum we are using for reference, i.e. the idea of inertial frames is necessary before moving on to force. Secondly, whilst in Newtonian mechanics force is viewed as the 'cause' of motion, modern field theories treat it more as a derived quantity, so to cover both contexts it becomes both 'cause' and 'effect'. If we treat force as an 'effect' in Newtonian mechanics, we end up with a circular argument defining mass. I think we can sacrifice rigour and retrict ourselves to the Newtonian world view. Sorry I can't help more, you are doing a great job. Gordon Vigurs 08:18, 8 December 2006 (UTC)

Correct definition of force

It was mentioned in the discussion already several times but obviously it did not help. In the article there is no note saying that correct physical definition of force does not exist. It would be also very useful to write two paragraphs about forces in QTF and GTR.

The article already contained a paragraph:

It is very important to mention that it is impossible to define force. All attempts in history failed because of definitions in circles. This is a reason why modern physics theories don't operate with the forces as the source or symptom of interaction. General relativity uses a conception of curved spacetime and Quantum field theory talks about exchanging of intermediate particles like photons, W and Z bosons or gluons. Both theories don't need force. However, because it is easy to imagine forces, one can compute them from these theories. But we must not forget, that correct definition of this concept does not exist.

It was denoted to be silly and removed. Perhaps it is not the best way how to express the fact but something like this should be included. It shouldn't be a problem to cite it, something like this is written in most of theoretical physics textbooks.

Please, consider it. Miraceti 15:36, 19 December 2006 (UTC)

As an undergrad with lots of physics (but my major was chemistry), I'm not sure this is a very productive argument. Force is a primary thing. We're all familiar with it as a physical fact of life, as a push or pressure or material stress. What good does it do to say it "really" doesn't exist? Of course it "really" exists. It's as "real" as anything else in your life or your experience. If you fall off a tall building and get squished on the cement, is it any use to say that it's not "force" that's smashing you, but an exachange of virtual photons? Does it hurt less. Or maybe even some even stranger Pauli exclusion "interactions" that opperate between electrons trying to be jammed into the same space? So what? It walks like a duck, quacks like a duck. We believe in energy, do we not? We believe in space, do we not? We have an unusual property of both, which we can feel with our hands and feet and butts, which happens to be the spacial gradient of work and energy in potential fields (like gravity, in this case). We need a name for it. And by gosh, we have one. SBHarris 00:35, 23 December 2006 (UTC)

Is this article about our believes, or about physics? Nobody says we should delete this article. Force is an important term because we use it in our everyday lives. However, a high-quality encyclopedia should mention everything important which is related to such a term. And impossibility of its correct definition is very important (besides this, it is very interesting). Miraceti 21:02, 12 January 2007 (UTC)

I do not see that that there is any impossibility in correctly defining force. Force is the spacial gradient of the energy (the Lagrangian). Or, if you like, force is the differential change with time, in momentum. Force is defined indirectly, but experienced directly, which is what leads to need to define it AS an entity. I guess I still don't see what your problem here is. What is it you believe is less "real" about force than about time, space, energy, momentum, or any other primary quantity? SBHarris 02:02, 13 January 2007 (UTC)

${\vec {F}}=-{\vec {\nabla }}V.$. That is correct. However, what is V? V is an potential energy. How do you define the potential energy? Please, consider that V is not just an energy, it would be simple then. (Energy is a physical quantity which is conserved in system invariant with respect to time. But this not our case. We need a definition of the potential energy.) Can you define the potential energy without the term “force”? Force is not defined indirectly, force cannot be defined at all! All definitions of force are only intuitive.

I am really sorry, I cannot direct you to some literature. I am on a long term work travel and the only literature which I have here is The Good Soldier Švejk. I am pretty sure, you can find it also in The Feynman Lectures on Physics. Feynman knew what Newton had known. Miraceti 12:34, 14 January 2007 (UTC)

No, the correct formula uses the Hamiltonian or Lagrangian T-V, which is not only potential but also kinetic energy. Obviously force may be used to increase kinetic energy only, no potential involved. Though potential cannot be defined at a point, differences in potential are real, and appear in QM equations all the time, where nature shows that the wavefunction senses them directly. And DIFFERENCES in potentials are just as useful in the equation you give above that defines force. So there you are. Energy differences are real and definable separately, without resort to use of "force." Does this answer your question? There are many definitions of energy which don't involve force. It's hv. It's mc^2. And so on. SBHarris 20:44, 14 January 2007 (UTC)

Well, ${\vec {F}}=-{\vec {\nabla }}V$ is correct when the total energy is conserved in the system. In general, it is really ${\vec {F}}={\vec {\nabla }}(T-V)$ (generalized force).

But there is another problem. You have to be able to measure distances if you want to use an operator ${\vec {\nabla }}$. Of course, you can measure distances in both, inertial and non-inertial frame of reference. In non-inertial frame of reference, you have to use "force" to be able use a real measuring instrument with finite rigidity (you cannot use light either, in such cases we would have to look at GR to explain why). In inertial frame of reference, you have to use "force" to be able to define the inertial frame of reference. Therefore "force" cannot be physical correctly defined in this way.

I hope, this helps a bit again. Probably, I should start from the end, from problems in inertial and non-inertial frames of reference. Sorry about that. Have you already tried to find it in Feynman?

BTW, this is not just a cosmetic problem. This is a fundamental problem which led to GR. Miraceti 23:05, 14 January 2007 (UTC)

I do detect a hint of Einstein in your argument there. If I read you right, your problem is not with the use of force in an everyday undergrad sense of it, as Newton defined it as the rate of change of momentum, but the fact that all these definition end up having a less then perfect deductive logic pedigree, right? Also while all force are field forces when seen at the microscopic level, is your concern more with field forces then with contact forces?Carl 22:34, 26 April 2007 (UTC)

Right! I have nothing against Newton and others. They knew what they were doing. Newton knew his definition was incorrect. This is not a problem which would disallow usage of the concept of force as Newton used it. The problem with definition of force is really deep and unavoidable - it is in a logic of definition.

I have a problem to comment your second question since "force" is a result of curved timespace in GR therefore it has not much sense to speak about "microscopic level". Also "field forces" have the same problem. It is not a problem of explanation why something moves with something else, it is a problem of definition of the term "force" itself. It cannot be avoided by definition of "field force". GR and QFT don't internally use "force" - it is not needed and it is used only in outputs because this concept is easy to imagine for people. "Force" would make these theories internally inconsistent.

I hope somebody will finally open the Feynman's lectures here soon. Miraceti 08:21, 25 July 2007 (UTC)

Electrodynamics and force

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)

Newton’s Three Laws

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)

Protection

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)

Virtual particles

It is better to say that particles intereact with each other via fundamental interactions than via the exchange of virtual particles. Feynman diagrams in which the virtual particles are drawn represent just terms in an asymptotic perturbative expansion. You cannot assign a well defined physical meaning to a particular Feynman diagram. Also, you don't necessarily recover the exact interaction when you sum over all Feynman diagrams to all orders. There can be non-perturbative effects (i.e. effects that are zero to all orders in perturbation theory). Count Iblis 22:01, 2 June 2007 (UTC)

Yeah, but "virtual particles" are a good answer to the question of what are electric and magnetic fields (other than those associated with ordiary photons) made of? What makes the antenna near-field different from the far field? Why do metal detecters and transformers only have such a short range? If quantum mechanics is valid, little chunks of these kinds of field are quantized. These chunks aren't conserved, but then neither are photons-- does that make photons non-real? SBHarris 22:09, 2 June 2007 (UTC)

Well, there are some people who think that particles don't really exist :) . But about virtual particles, I think it's better to turn things around. In quantum field theory the fundamental objects are the fields. The particles arise when the fields are quantized. I.e. if you have a free field, you find energy eigenstates of the form E_k = (n_k+½)h-bar omega_k, for each wavevector k of the field. This state is intepreted as a state containing n_k particles with momentum k and energy omega_k.

Suppose you have two fields F1 and F2 that couple to each other. A quantum of the field F1 (F1-particle) can exhange energy and momentum with another F1-particle via the field F2. I.e. an initial state |k1,k2> representing an F1 particle with momentum k1 and one with momentum k2 can evolve to |k1',k2'>. But there is no real intermediary state for the field F2 through which it passes.

It's just like tunneling in ordinary quantum mechanics. If you have two states with equal energy that are coupled to each other via a third state with a higher energy, then the system can make a transition even though it hasn't got the energy to make it to the third state. You can say that the third state is entered virtually in the transistion, but it's not a real physical state. A real physical state does exist but it isn't accesible to the system. But the mere fact that it does exist, even though it cannot be reached, is enough for the system to jump from one to the other state. Count Iblis 23:57, 2 June 2007 (UTC)

A lot of physicists feel only the fields are real (Weinberg seems to feel that way), and particles are just field excitations. Which leaves open the curious question as to why various massive particles always have the SAME mass when detected. I think however, that Feynman felt just as strongly that only the particles are real, and "fields" are ghosts-- sometimes seen only by the forces they exert when composed of particles with too little energy to be detected individually (ie, "real"). But forces do have a certain undeniable reality, as I've noted. They hold you in your chair but keep you from going through it. They hold nucleons and nuclei together. They make chemistry. All that, mediated by interactions of particles which (mostly) can't ever be detected as particles. Even though modeling them as particles (Feynman's diagrams) seems to be the only way to simplify the fields enough to figure out what they do (at least for strong fields, or exact effects of weaker fields). Dr. t'Hooft, for one, thinks the diagrams contain more truth than the equations they diagram. And the diagrams show virtual particles as the equation pertrubation terms. SBHarris 00:50, 3 June 2007 (UTC)

Fixing some problems in the intro

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)

If we consider this as an article and not a text book then I think we should use the journalistic rule of thumb of the 5W's as a guide. What I find missing in the intro is when does force exist. In other words forces exist when particles of matter have certain features or qualities. Someone can probably phrase this better and more accurately but I think you get the idea.

--RobertJDunn (talk) 18:34, 2 January 2008 (UTC)

Conservative vs. non-conservative forces

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)

Revision of definition section

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)

Dissident view

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 [1].

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))

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)

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)

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)

Missing Definition?

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)

please fix

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)

Thanks, the new revision is looking great!-- Penubag  08:59, 8 November 2007 (UTC)

Nuclear Forces

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)

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)

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)

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)

Introduction

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)

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)

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)

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)

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)

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)

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)

Free-body Force Diagram

The diagram showing the free-body force diagram of a block on an inclined plane seems poorly constructed to me. Generally, you shouldn't put both the weight and its components on the same diagram - that is essentially doubling the weight. Usually, if both are on the diagram, the components are drawn in such a way (like with dotted lines) to indicate that they are not in addition to the weight itself. It seems like a minor point, but one which I've found is misleading to students. PhySusie (talk) 09:21, 22 November 2007 (UTC)

I have created a new image of the free-body diagram and have replaced the old one. Hopefully that should clear things up. -- Penubag  20:57, 25 November 2007 (UTC)

It's certainly an improvement, but might it be better to split the image up into three different ones? ScienceApologist (talk) 14:06, 27 November 2007 (UTC)

I'm going to have a new version of the freebody diagram in a few weeks with these improvments:

• change Ff = μk F N to Ff=μkFNcosθ
• make the multiplication symbol not look like the variable x
• change the word "triangle" to "incline"
• maybe add motion to the static top image (should I?)

I don't know if I should split the images like you suggested, it would be hard working that into the article, do you have any other suggestions?-- Penubag  08:40, 4 December 2007 (UTC)

Thanks for your work on this, Penubag. Here's a few suggestions: Ff = μkmgcosθ is incorrect. Multiplying FN by cosθ is actually wrong because it opposes the friction force law which applies for all situations (that Ff = μFN). What is true is that FN = mgcosθ for θ measured at the bottom of the incline, so maybe you were confusing your normal force with gravity. Also, adding motion will probably confuse the diagram. I would say, instead, we should be ambiguous about which μ we are using and whether it is in static or dynamical equilibrium since it could be either given the right circumstances. Thus, my recommendation is to use the formula: Ff = μmgcosθ or simply Ff = μFN and let the reader do their own trigonometry. Also, it isn't often that someone measures the angle from the top of an incline, so getting rid of that treatment might be advisable as well. ScienceApologist 16:04, 4 December 2007 (UTC)

The new diagram does look better - thank you. However, the original problem still remains. The weight vector and its components are on the same diagram - which can be misleading. Also, visually, the components don't match the vector (don't line up in terms of length I mean). Perhaps the second diagram down could show just the weight vector itself (along with friction, etc.) and the third diagram down could show just the components of the weight (along with the friction, etc.). This would demonstrate the explanation in the text I think. Anyway, I appreciate your work on this.

PhySusie (talk) 00:37, 6 December 2007 (UTC)

new version

I uploaded my completed image, which addresses all concerns. I included both the trig and the N for normal for the viewer (because if you are learning trig and physics at the same time, as a highschool student, this greatly helps), I got rid of the bottom unneeded image, added additional information to help young learners, and addressing Physusie's concern, I made the 2 Fparallel/perpendicualr appear semi-transparent as they add up to the N. Hopefully this image best suits this article. Thanks, hope this helps, then again, if there are additional improvements to be made, write them here.-- penubag  05:04, 15 December 2007 (UTC)

The new diagram definitely looks better - thank you. However...I hate to say this...there is a little mistake. In the lower diagram, you have an equation that has N and underneath it in parentheses you give it as equal to the sin component of mg instead of the cos component. You have the sin and cos components labeled correctly on the diagram, so I think its just a typo. Also, in reference to something you wrote before, it might be better (though not critical) to get rid of the x's in the component equations. At first glance it does look like you are multiplying by x there. Thanks for all the work - it really does look a lot better.PhySusie (talk) 13:14, 15 December 2007 (UTC)

Oops, yes, there was a typo, but it should be fixed now. I further decreased the size of x so it looks more like the multiplication symbol rather than the variable. Thanks for catching the errors. -- penubag  22:41, 15 December 2007 (UTC)

Awesome - looks fantastic! Thanks! PhySusie (talk) 01:35, 16 December 2007 (UTC)

I'd also like to thank Penubag for his work on this image. I do have a few (nitpicking) comments though:

1. the vector representing the force of gravity is labeled as weight. This is technically not the weight of the object as the weight is the response to the force of gravity. A better vector label would be "Gravity".
2. in the second figure, the vector representing gravity is muddled with the bottom of the inclined plane. It might be better if we made that vector short enough so that it didn't cross the horizontal line.
3. the dotted lines do not precisely correspond to the heads of the component vectors.

As I said, these are really nitpicky points, but I think addressing them might improve the image. Again, thanks Penubag for your work on this. ScienceApologist (talk) 17:31, 16 December 2007 (UTC)

You're welcome Physusie and SA. I'll get this image perfect! Well I just uploaded the new free body diagram. As response to SA, in most all Physics text books I have read, I have always seen the force of gravity labeled as weight. Just in case, I have done an image search and found myself to be correct. However I have added Fg*m=W for your sake onto my diagram. Hopefully, this should address your concerns.

As another thing, I spent at least an hour trying to get my dotted lines lined up. It just wouldn't happen, so I replaced them with a line containing a gradient to become transparent...at least the reader gets the point one way or the other, right?

Thanks for you continued input. -- penubag  06:42, 20 December 2007 (UTC)

I'm afraid that "weight" is one place where most physics texts get it wrong. Imagine an object in free-fall. It is considered "weightless". Yet the force vector due to gravity is still pulling on it. Clearly a weightless object cannot have a non-zero weight. It's our conventions that are screwing us up. In reality, the only time you have "weight" is when you have a force that is responding to gravity. In most situations, the force responding to gravity happens to be the equal in magnitude to the force of gravity itself. On the inclined plane, however, this is not the case. We have a chance to make this figure better than many found in physics textbooks.

One more thing: the vector really shouldn't be Fg*m = W as that isn't unitarily correct. It should instead be m*g where g is the acceleration due to gravity.

Otherwise, it's looking really good. Maybe you should replace the image on free body diagram as well?

ScienceApologist (talk) 07:56, 20 December 2007 (UTC)

One more suggestion: you could probably get rid of the dotted lines connecting the vector to its components all together. They really don't add much to the picture as they are not vectors themselves. Sorry you spent an hour on that task. We really do appreciate your work. ScienceApologist (talk) 07:59, 20 December 2007 (UTC)

Ah, I see, but wouldn't this confuse people, seeing vectors being split out of Fg, and most readers of this article (mostly students) would probably have seen an image like this in their textbooks and then seeing this one may further confuse them. I would say that we should leave it at Fg, since that's what our society has made it, also considering many other mistakes society has made, but still leaving them as is just for clarity (the Fahrenheit scale or English system as a quick eg). But, since you primarily wrote this entire article, I'll leave this decision up to you. I'll fix the other 2 concerns after the decision, and, I'm going to replace that image on the freebody diagram article with an entirely different one, after I'm done with this image.-- penubag  09:14, 20 December 2007 (UTC)

Using Fg seems like a fine compromise to me. We just cannot have m*Fg which is not a force. ScienceApologist (talk) 14:32, 20 December 2007 (UTC)

Okay, so, please tell me specifically which things I should change. So far, I have:

1. m*Fg --> Fg should I change the top image too?, and do I only replace the small text (the m*fg) or the whole vector (the W and everything to Fg). Maybe should I just replace Fg*m to m*g?
2. get rid of dashed lines

Thanks again for your input-- penubag  16:46, 20 December 2007 (UTC)

I think replacing Fg*m to m*g is fine. Changing the top image too is a good idea. I'll leave it up to you whether you replace the whole vector or just the small text: it's not really that important. Thanks for doing this, ScienceApologist (talk) 01:09, 27 December 2007 (UTC)

GA quick fail

This material needs to be cited via inline citation. Although it does not require the level of citation outlined in WP:V, it does require the level outlined in Wikipedia:Scientific citation guidelines. Each section or paragraph needs to direct readers to the appropriate source for verification and further information. Thanks. Awadewit | talk 10:39, 2 December 2007 (UTC)

The article content can be found from any textbook you care to name. Thus, I have cited them as such. ScienceApologist 02:46, 4 December 2007 (UTC)

A slapping of a footnote listing a number of different textbooks, with no page references from any of them, not offered in support of any specific statement, at the end of each paragraph of the article, is not proper referencing by any stretch of the imagination whatsoever.

Clearly, this article can never be a "Good Article" as long as any such nonsense remains here. Gene Nygaard (talk) 22:56, 4 December 2007 (UTC)

Then again, maybe it can be. It wouldn't be the first article made worse with badly done over-referencing in this process. Gene Nygaard (talk) 22:59, 4 December 2007 (UTC)

I'm not opposed to removing the references if you can convince those who think that every paragraph needs a reference that this kind of advocacy is misplaced. ScienceApologist (talk) 19:45, 5 December 2007 (UTC)

GA On Hold

The article does not mention absence of a correct definition. Since this is a fundamental problem of the "force" concept, it must be added if the article should be among good ones. Miraceti 20:00, 4 December 2007 (UTC)

This comment almost doesn't make sense. The article deals extensively with how force is defined. ScienceApologist 20:24, 4 December 2007 (UTC)

And it does not mention that a correct definition is impossible since all are circular definitions. Miraceti 20:53, 4 December 2007 (UTC)

Just try it. And remember that inertial frame of reference needs force in its definition. It is not an accident that force is missing in both, the GTR and QFT. Force would make them inconsistent. Miraceti 21:08, 4 December 2007 (UTC)

See [2] and also [3] and The Feynman Lectures on Physics, vol. 1, chapter 12.1 are interesting. Miraceti (talk) 21:28, 4 December 2007 (UTC)

These issues are all already addressed in the article. It is up to you to make an explicit recommendation. Keeping a nomination on hold simply because you don't think something is present that other editors do believe is present is a bit obstructionist, in my personal opinion. ScienceApologist (talk) 19:43, 5 December 2007 (UTC)

Could you show me where it is? It was there but it was removed. If any remnants remained, I would be pleased to find them. A quote would be enough. Thank you. Miraceti (talk) 18:01, 7 December 2007 (UTC)

The definition of force is sometimes regarded as problematic, since it must either ultimately be referred to our intuitive understanding of our direct perceptions, or be defined implicitly through a set of self-consistent mathematical formulae. Notable physicists, philosophers and mathematicians who have sought a more explicit definition include Ernst Mach, Clifford Truesdell and Walter Noll.

Hope that suffices. ScienceApologist (talk) 18:19, 7 December 2007 (UTC)

I see that. But:

1. It is not "sometimes" regarded, it is _always_ impossible to defince a force.
2. It is in a section "Newton's second law" which looks like the definition is problematic when N2L is used. But it is always impossible, not only in case of N2L.
3. There is no mention about avoiding this definition in modern theories.
4. Also two examples of circle definitions would help.

I believe we will find out how to deal with this issue. I consider it to be so fundamental that it needs a longer explanation than a short, uncertain note in one of the paragraphs. I understand this is not important for many people since everyone can "push" and it seems to be so simple but it is very important for understanding the concept. I guess a good Wikipedia article should provide a text which allows it. Miraceti (talk) 23:51, 8 December 2007 (UTC)

I think there may be something of a language barrier here because a lot of what you are saying doesn't quite ring true grammatically. What I will say is that your objections are not substantive and seem to be based on a very particular perspective you have on the subject. While the term interaction is often used instead of force in modern physics as the fundamental ideas that describe gauge boson-mediated events to avoid confusion with older definitional constraints, there are plenty of people who use the term "force" interchangeably. The texts we cite do just that. So now, I'm going to have to ask you to cite some texts to support your claim that force's definition is so circular as to be stridently impossible to make. Even your attempt to cite Feynman doesn't make much sense as he himself provides a framework for the definitions we outline. ScienceApologist (talk) 23:16, 10 December 2007 (UTC)

I have to agree with ScienceApologist; I can see Miraceti's point that there are problems with circular definitions of force, but I don't believe this deserves mention in this article beyond what is already there. The concept of Force remains (as with much in science) a useful problem-solving tool, and that is what this article addresses. Perhaps, if he feels this is an important issue, Miraceti could write a separate article dealing with defninition and inertial frame-of-reference problems? EyeSerene^TALK 11:14, 11 December 2007 (UTC)

I cannot provide another cites except those I already have given since I don't have the original source anymore, my studies of theoretical physics are over and I live abroad. I can try to look for it but it will take some time, sorry. (I remember it from a textbook so it exists. I am pretty sure that any better theoretical physicist can confirm it.) I know there is the note you have cited in the article. But it does not say why forces are not actually included in QFT. It is actually very unclear for a person who wants to get to know something fundamental about "force" - it says more about people than about forces. And it says nothing about forces in GTR.

I do not see much reason to create a new article. The thing is simple and it can take only a few lines, may be three paragraphs including examples.

It is difficult to understand that you don't see the problem. The article does not provide any precise and correct definition of "force". Obviously, it cannot do it. But there is no explicit explanation why it cannot be provided. The article actually does not say what force is. It says much about what kind of forces we use, how we represent them and how we deal with them. But practically nothing about their nature. It's strange that it should be nominated among the best articles. It is like an article about a car without a statement "It is a wheeled passenger vehicle that carries its own motor" but with a messed list including Porsche and truck and statements that people like to use it because it is simple and some people get confused when they use a railroad car. Miraceti (talk) 19:22, 11 December 2007 (UTC)

Except you aren't really explaining what you would like to see that is different. The article as it currently exists does deal with forces in GR and in QFT. So I'm at a total loss as to what kind of content you are looking for in these "three paragraphs". ScienceApologist (talk) 21:18, 11 December 2007 (UTC)