Talk:Reactive centrifugal force/Archive 1

Reply to Wolfkeeper
Wolfkeeper, there is no need to have this separate article. There is only one centrifugal force. The example that you give is exclusive on a number of counts.

(1) It concentrates on situations in which the centripetal force is supplied by an inward pressure from a contact object. David Tombe (talk) 05:59, 27 April 2008 (UTC)


 * Yes. That's because it applies there. In the case of the car and the rider, the car experiences the centrifugal force. In the case of a cyclist on a banked track, the track experiences the centrifugal force.- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

What about the other kinds that you have ignored?

(2) You ignore the fact that if the centripetal force were a tension from a string, then it would be the centripetal force that is the reactive force. David Tombe (talk) 05:59, 27 April 2008 (UTC)


 * No, I don't think it is referred to in that way.- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

You have totally ignored the tension in the string scenario.

(3) You ignore elliptical motion. David Tombe (talk) 05:59, 27 April 2008 (UTC)


 * Considering I was the one that put the center of curvature argument into the article, no.- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

Then why write circular motion in the disputed paragraph?

(4) You ignore forces caused by gravity, electrostatics and the Lorentz force.

Do you not see that whether consciously, or sub-consciously, you are trying to write centrifugal force and the Bucket argument out of the literature? David Tombe (talk) 05:59, 27 April 2008 (UTC)


 * LOL. If I'm doing something sub-consciously, then I wouldn't see it would I?- (User) WolfKeeper (Talk) 07:14, 27 April 2008 (UTC)

So basically, you are admitting that you have ignored these forces.


 * No, basically I'm laughing at you David.- (User) WolfKeeper (Talk) 21:16, 28 April 2008 (UTC)


 * Reactive centrifugal forces don't appear in every physics problem. In the case of two bodies orbiting their barycenter under gravity, electrostatic or magnetic forces I can't see that any reactive centrifugal force exists per se, and quite frankly, I don't really care.- (User) WolfKeeper (Talk) 21:16, 28 April 2008 (UTC)

I see. So you are only concerned with the tension that the centrifugal force causes in the string and the reactive centripetal force that the tension causes. In that case, you have got the terminology the wrong way around. David Tombe (talk) 08:20, 29 April 2008 (UTC)

Wolfkeeper, your example, which is actually Rracecarr's, is too exclusive. You have ignored the fact that centripetal force is the reaction force when the the motion is being caused by tension in a string. You have ignored all the points above. David Tombe (talk) 08:12, 27 April 2008 (UTC)

There are no such things as fictious and reactive centrifugal force. There is only centrifugal force. —Preceding unsigned comment added by 72.64.52.209 (talk) 14:22, 28 April 2008 (UTC)

FyzixFighter's reference to the 1996 Oxford Dictionary
FyzixFighter, What does the 1996 Oxford dictionary actually say in relation to limiting a description of centrifugal force to involve only circular motion, and pressure contact forces?

There is no evidence that your contribution here is anything other than to back up a team. It is team vanadalism. Somebody has sent for your assistance because you normally write about other topics. At the moment you are defending a very amateurish paragraph and you are simply playing out a superior numbers game. David Tombe (talk) 15:32, 28 April 2008 (UTC)


 * Paraphrasing, the source merely says that the general use of the term "centrifugal force" is to refer to the fictitious force that appears in non-inertial frames, but that it can also be used to describe the 3rd law pair, reactive force that is exerted on the source of a centripetal force. Where is the mention in the original version about contact forces? All I can see is a mention of Newton's third law. Nobody sent for me. I am not part of any team, and have had no previous or current dialog or contact with the other editors. I do occasionally edit physics related articles if you look far back enough in my history - in fact, I think I ran into you about a year ago on one of those pages. --FyzixFighter (talk) 16:09, 28 April 2008 (UTC)

FyzixFighter, In the example that you keep reverting, it talks about 'an object' causing the centripetal force. The only examples that I can think of under that description is a tense string or the floor of a rotating cylinder.

The example doesn't cater for gravity, electrostatics, or electromagnetism.

In the tension in the string example, the centripetal force is reacting to the centrifugal force. If there were no centrifugal force, then there would be no tension in the string. So the whole 'reactive' thing is wrong.

I have tried to re-word it more generally.

Can you please point out your exact objections to my re-wording. I had generalized it to cover all kinds of curved path motion.

If you would deal with the issues instead of just mindlessly reverting and making false accustations against me on the wikipedia administrator's notice board, then it would all end up with a more positive conclusion.

What we are aiming for is an article which is accessible to a broad range of readership.

I really do believe that the reactive centrifugal page has to go, because it is totally confusing the whole issue as well as being inherently wrong.

On a recombined page, it can then be discussed as to what centrifugal force actually is.David Tombe (talk) 08:16, 29 April 2008 (UTC)


 * FyzixFighter, before you revert again, can you please explain exactly what is wrong with the simple sentence that I have inserted. It describes every aspect of centrifugal force in one sentence. There is no need to involve Newton's 3rd law in the discussion.David Tombe (talk) 14:18, 29 April 2008 (UTC)


 * (after edit conflict) Saying 'an object' causes the centripetal force is perfectly valid and does include gravity and electromagnetic forces - when you get down to it, the contact force that you want to limit this statement to is an electrostatic repulsion. As for the term 'reactive', please see reaction (physics) to see that 'reactive' in this sense does not imply one causes the other. The two forces are simultaneous, and occur because every force has to have and equal and opposite force as described by newton's 3rd law of motion. Also, see "McGraw-Hill Dictionary of Physics" pg57 (1984 ed) which calls this the "reactive centrifugal force". Your previous rewording completely changed the meaning of the sentence - it removed the 3rd law action-reaction coupling of the two forces, and said that this centrifugal force acts on the same object that the centripetal force is acting on, which is not true. Again, here we're talking about a centrifugal force that is a reaction to the centripetal force, and therefore the two forces are not acting on the same object. They can't be if they are the action-reaction forces being described in Newton's 3rd law of motion.
 * As for my "false accusations", I have not wikistalked you - I have not followed you around to other articles with the intent of causing distress. You apparently have:    . Or is there some other reason for these edits of yours? I gladly invite any administrator to look at my edits and yours and let them judge who is wikistalking.
 * While we are trying to make this accessible to a broad range of readers, we are also trying to make it based on reliable sources. You have to provide one reliable source support your interpretation of physics. The other editors and I, on the other hand, have relied on modern physics textbooks and other academic sources. But I do agree with you that the two articles should be merged as the "reactive centrifugal force" is more footnote to the centrifugal pseudo-force of non-inertial reference frames. --FyzixFighter (talk) 14:25, 29 April 2008 (UTC)


 * FyzixFighter, You seem to be concentrating on a specific circular motion scenario in which an object is causing centripetal force by pushing on another object. That would have to be something like inside a rotating cylinder.


 * But in any case, it is the centripetal force that is reactive and not the centrifugal force. The cylinder floor only pushes inwards in response to the outward inertial force. It's exactly the same with gravity and normal reaction. Normal reaction of the ground is the reaction force.


 * Quite frankly this particular article is a mess and we are arguing to re-word something in relation to an article which we both agree should be closed down.


 * But it might not be closed down. And in the meantime we need to have some basic statement about what centrifugal force is. We can't confine it to circular motion. We can't confine it to contact push forces.


 * So can you think of a better sentence to cover the key points. The key points are (1) Curved path. (2) Outward force. And that's about the height of it.


 * But it should really be in the introduction to a general article on centrifugal force.


 * Regarding your other points, I distinctly did get the impression that you were wikistalking me. You arrived in this edit war by reverting my edits and you have been continuing to do so. You don't revert edits by other people and you needn't try and claim that they are better edits. You wouldn't dare have reverted Wolfkeeper's splitting of the article even though you disagred with it. You would have told him your views politely and given him credit for his motives and suggested to him nicely that maybe he might revert back again.


 * You didn't even enter the discussion until I approached you directly.


 * It is obvious that you are in some kind of understanding with Rracecarr.


 * But underlying all of this, although never explicitly spoken, is the desire of all of you to play down any information that might point to centrifugal force as being real.


 * Although the controversy doesn't have to enter the introduction, you don't want to have a clear exposition of the centrifugal force in the introduction. You want to emphasize in the introduction your belief that the centrifugal force is fictitious and that it is the product of observing things from a rotating frame of reference.


 * But you must also be aware of the fact that the centrifuge effect is real and that it is observable from all reference frames. You must know that. How could you not see that?


 * Yet for some reason you are very keen to play it down. Did you actually see the introduction that I wrote that triggered this edit war off?David Tombe (talk) 19:37, 29 April 2008 (UTC)


 * Your perception of being wikistalked does not excuse your edits (that I listed above) in an attempt to distress and disrupt other editors. Or, again I ask, what was your reasoning for making those edits?
 * I've only reverted edits that were in stark disagreement with reliable sources. Wolfkeeper's split, while I didn't fully agree with it, did have some basis in some reliable sources and so I had no overt reason to oppose it. Also, in cases like those, I like to give the idea some time to marinate in my mind before coming to a decision. And again, if it's so obvious that I am in some kind of understanding with Rracecarr, then why am I not aware of it.
 * You're still misunderstanding the use of the term reactive. Saying a force is reactive to another force does not mean that one causes the other. Also the normal ground force is not the reactive force to the force of gravity. The normal ground force is the reactive force to the object pushing on the ground. The reactive force of gravity is the force of gravity from the object on the earth. I also do not see how the current wording limits it to contact forces - Newton's 3rd law applies as much to gravity and electromagnetic forces. For planets in orbit about the sun, the reactive force to the centripetal force of gravity acting on the planets due to the sun is the force of gravity acting on the sun due to the planets. I do think that the we may need to generalize this to curved paths, but every time you add that edit in, you change far too much like removing the mention of Newton's 3rd Law and changing what the centrifugal force is acting upon (the object experiencing the centripetal force versus the object exerting the centripetal force).
 * We are not playing down any information that might point to centrifugal force as being real, mainly because you have not provided any. You have invoked common sense, but no reliable sources. Other editors and myself point to reliable sources, such as physics textbooks and other academic sources. Where are your reliable sources? All the behaviors that you bring up, such and cyclones, hurricanes and centrifuges can all be explained in the inertial reference frame without resorting to the invention of a centrifugal force as you describe it. --FyzixFighter (talk) 20:12, 29 April 2008 (UTC)

FyzixFighter, You keep missing the point. My edits have never contradicted the official position. I don't need reliable sources to state that a centrifugal force is the outward force that occurs when an object moves in a curved path. So you never had any basis to delete those edits.

You are making out falsely that I have been trying to put controversial material into the main article.

You also miss the point about cyclones and centrifuges etc. I know that all those effects can be explained by inertia.

All I was saying was that they are real effects. They can be viewed from space. None of those effects needs to be viewed from a rotating frame of reference but the articles are pushing the line that these effects can only be viewed from rotating reference frames.

It is clearly not true. They are real effects. Call it inertia or centrifugal force, but they are real effects. When large particles push through smaller particles, that is a real effect viewable from any frame of reference.

Your side are trying to avoid a simple description of centrifugal force and to cloud up the introduction with statements such as that centrifugal force is something that can only be observed from a rotating frame of reference. And that is clearly untrue.

And you are twisting all that about the object causing the centripetal force. The centripetal force is the reaction force. There is no doubt about that. The centrifugal force is the outward acting force.

And you further twisted the bit about the object. The article clearly mentions an object, so clearly it is not talking about gravity or electromagnetism. I suppose you might want to argue that pressure comes from electrostatic repulsion at microscopic level. But the truth is you have been deleting good edits and replacing them with bad edits for no other reason than to support a team.David Tombe (talk) 20:32, 29 April 2008 (UTC)


 * I never said the effects weren't real, just that the cause of the effects do not require the inclusion a centrifugal force. When writing out the sum of the forces to do F_net=ma (which is only valid in inertial frames) to get the equations of motion, there is no centrifugal force term there. Inertia is not a force as defined by any reliable sources or in any of the academic literature.
 * Further, to provide a quote of the material a paraphrased above from Oxford's "Dictionary of Physics":
 * Occasionally the concept of a centrifugal force can be useful, as long as it is recognized as a fictitious force. A true centrifugal force is exerted, as a reaction, by the rotating object on whatever is providing its centripetal force.
 * I cross-references the term "reaction" to a definition similar to the one found at reaction (physics). --FyzixFighter (talk) 23:24, 29 April 2008 (UTC)


 * FyzixFighter, what name would you like to use for the effect that occurs in a centrifuge? And is it a real effect? David Tombe (talk) 12:53, 30 April 2008 (UTC)


 * It's irrelevant what name I would like to use. What effect does the academic literature call it? From the sources I've looked at, they refer to the process as sedimentation. That effect is real - no argument there. Our disagreement is what causes the effect. A centrifugal force only appears when one naively tries to apply Newton's second law to a rotating frame (it's only valid in inertial frames, see Hand & Finch "Analytical Mechanics, pg 267). When the physics is done in the inertial frame where Newton's 2nd is valid, no centrifugal force term appears in the sum of forces, and therefore one can get the same effect without introducing a centrifugal force. At least, that's what I've seen in all the reliable sources I've checked.
 * Again, inclusion isn't determined by whether or not the physics makes sense to every editor; it's determined by reliable sources. Do you have a reliable source that says the effect is caused by a real, non-pseudo centrifugal force? --FyzixFighter (talk) 13:14, 30 April 2008 (UTC)

FyzixFighter, I see. You are denying that the centrifuge involves centrifugal force. You are totally out of line with the general understanding of the term centrifugal force. You are trying to introduce some mathematical meaning for the term that has totally lost touch with the original meaning.

In that case, in what topic would we deal with things such as the centrifuge, Newton's bucket, and people getting flung to the side door of a swerving car? David Tombe (talk) 13:33, 30 April 2008 (UTC)

David: what you are calling 'real centrifugal force' I would call 'inertia.' The object which seems to be experiencing an outward force is only reacting against a centripetal force acting inwards. Granted that's a subtle point, but every textbook on classical mechanics I've read expresses it in a similar fashion. I've got to side with FyzixFighter on this. I'm not surprised by your disagreement, because the physicist's definition of 'centrifugal force' is not the same as the lay definition, therefore the confusion. A better explanation in the article would be a good thing, but it's hard to do because the difference is subtle. (And before you raise the argument, inertia can kill you, too.) Plvekamp (talk) 14:22, 30 April 2008 (UTC)


 * I'm not denying that the centrifuge involves centrifugal force, every reliable source I can find is denying it. To quote one of them, the centrifugal force, Coriolis force, and Euler force "aren't real forces; they are purely kinematic consequences of the rotation of the body coordinates." When the physics is done right, applying Newton's 2nd law in the inertial frame where it is valid, none of those three forces show up in the sum of the forces, and yet the observed effects are predicted. Again, when the physics is done right, the behavior seen in the centrifuge can be explained without involving a centrifugal force.
 * All those situations you mention deal with a rotating frame, and therefore the centrifugal (pseudo)force and should be handled there. This article is to deal with the true centrifugal force that the moving object exerts on the source of the centripetal force, forming an action-reaction pair as predicted by Newton's 3rd law. Of course, this only occurs in some instances, since when considering gravity and orbital motion both forces in the action-reaction pair are centripetal.
 * Again, where is your reliable source that the centrifugal force in those situations is a real force and not a pseudoforce? --FyzixFighter (talk) 14:52, 30 April 2008 (UTC)

Plvekamp, I would agree with you that inertia is effectively the same thing as the parent effect of both centrifugal force and Coriolis force. But let's keep this discussion to centrifugal force. Supposing inertia and centrifugal force are the same thing, and supposing it is an absolute real effect as can be seen by the diffusion effect in the centrifuge. Then we are merely splitting hairs if we try to limit the application of the term centrifugal force to the situation as when we view it from the rotating reference frame. It is silly to say that it is centrifugal force as far as a man riding in the centrifuge is concerned, but that the man sitting in the corner of the room is not allowed to use that same name.

There are other complications which I am trying to sort out as well. This business of reactive centrifugal force doesn't need to enter into the discussion. When the heavy particles in a centrifuge are accelerating out to the edge, they are experiencing centrifugal force. When they reach the edge, a centripetal force constrains them to circular motion in conjunction with the centrifugal force. We have an action-reaction pair. But this is an extension of the core issue and doesn't need to be discussed in the introduction.

Anyway, that explains why I wanted to drop rotating reference frames from the description altogether. They are superfluous to requirements as far as decsribing the actual effect is concerned.

But there are some editors here who are very much focused on the mathematical equations for transformation to a rotating frame of reference and they are very adamant that the term centrifugal force should only ever be applied inside the rotating reference frame.

The next question surrounds the issue of whether centrifugal force is real or fictitious. Well simply saying that it expresses the effects of inertia in the rotating frame doesn't make it fictitious.

But the problem gets more complicated. We then enter into the Bucket argument which in my opinion is a variation of the Faraday paradox. Is the radially outward effect that causes hydrostatic pressure in the bucket of water the same situation as when we view a stationary bucket of water from a rotating frame of reference?

I say that it is not the same. The latter effect is totally fictitious.

But by using the maths for rotating reference frames, there is a school of thought which believes that these two effects can come under the one mathematical umbrella and that hence we can formally declare centrifugal force to be fictitious always.

This is a gross error in my opinion. The stationary bucket is not the same as the moving bucket with the centrifugal hydrostatic pressure. One is a fictitious effect and one is a real effect.

So how do we word the introduction? Well we have to find a compromise between the modern precise mathematical terminology and the understanding of the term by the man in the street. We have to concentrate on the real effect. David Tombe (talk) 17:19, 30 April 2008 (UTC)


 * FyzixFighter, I think that you are missing out on the subtelty of the Bucket argument. Even if we restrict the term centrifugal force to rotating reference frames, forgetting about this so-called reactive centrifugal force, there will still be two kinds of situation to contemplate. It's the Faraday paradox. Is the situation of co-rotation in which an outward radial pressure occurs, the same as the situation when the object sits stationary and we view the artificial circle from the rotating frame.


 * You may argue that both situations are united under the same umbrella maths. But you could say that about the Lorentz force too in relation to the Faraday paradox. I personally believe that the maths in question is only correct, and was only derived to cater for co-rotation, and that its application to the stationary object is heavily flawed. But that doesn't matter. Put the maths aside, and it is still obvious that the physics of the two situations is different.


 * You need to appreciate that there are two distinct physical situations to contemplate. And only one of them is centrifugal force. Call it inertia if you like, but only one of those situations is inertia/centrifugal force.


 * So you can't introduce centrifugal force under the allegation that it is fictitious. What you do is, you describe it in the introduction and discuss the controversies in the article. David Tombe (talk) 17:31, 30 April 2008 (UTC)


 * Sorry, no. I'm basing my arguments not on my personal understanding of physics, but on reliable sources. You're trying to introduce original research ("I personally believe..."). Where is the reliable source that says the centrifugal force is not a pseudo/fictitious force but a real force as you describe? Until you provide one, the introduction will introduce the centrifugal force as it is described in the reliable sources, as a kinematic consequence of a rotating frame and not a real force. --FyzixFighter (talk) 17:41, 30 April 2008 (UTC)

FyzixFighter, so many sources describe it in different ways, and collectively they illustrate that there is great confusion over the term.

We don't need a source to confirm that the effect that takes place in a centrifuge is real. We can see it so clearly without needing a written source to confirm it.

Can you actually appreciate that there are two distinct effects as per the Bucket argument. One is an outward radial pressure that is real, and the other is an artifact circlular motion as in the diurnal rotation of the celestail sphere?David Tombe (talk) 18:28, 30 April 2008 (UTC)


 * No, the sources do not describe it in different ways. All reliable sources describe this as a pseudoforce, ie not a real force. I'm not asking for a source for the fact that the effect in a centrifuge is real. I'm asking for a source that the effect is caused by a real centrifugal force and not a pseudo centrifugal force. This is really quite simple, all you have to do is provide a reliable source that the centrifugal force is a real force. Until you do, the changes you want to add violate WP:OR,WP:RS, and WP:FRINGE. --FyzixFighter (talk) 18:36, 30 April 2008 (UTC)

FyzixFighter, now you are just being silly. If the centrifuge effect is real, then the centrifugal force is real. No textbook citations are necessary to prove this fundamental fact.David Tombe (talk) 18:41, 30 April 2008 (UTC)


 * Whether or not that is so, within the wikipedia, unreferenced material can be removed at any time.- (User) WolfKeeper (Talk) 19:53, 30 April 2008 (UTC)

Wolfkeeper, under wikipedia rules, obvious facts don't have to be referenced. And anyway, there were no unreferenced facts in my latest writing of the introduction. You reverted as a knee jerk reaction, on the assumption that I had written a clause stating that centrifugal force only occurs during co-rotation. When you realized that you had read it wrongly, you dug in nevertheless, and to save face you are now trying to deny hydrostatic pressure in a rotating bucket.

You have demonstrated that you are not in a position to be editing articles about real physics. David Tombe (talk) 09:44, 1 May 2008 (UTC)

Misleading inaccuracy had slipped in - compare with old version
Compared to the old full article http://en.wikipedia.org/w/index.php?title=Centrifugal_force_(rotating_reference_frame)&oldid=196032047 regretfully at least one misleading inaccury had slipped in, together with the removal of a reference that avoided that inaccuracy. I now corrected that and will put the reference back. There may well be other new errors or erroneous suggestions. -> please compare the two versions to check this article. Harald88 (talk) 13:02, 28 September 2008 (UTC)


 * If you use polar coordinates in an inertial frame a term appears that is called 'centrifugal force/acceleration' and another called 'coriolis force/acceleration'. Are these not fictitious forces?- (User) Wolfkeeper (Talk) 14:13, 28 September 2008 (UTC)


 * They are, but not according to the point of view that centrifugal force must vanish in an inertial frame. Calling the polar coordinate term r&omega;2 a centrifugal force, where &omega; is not the rotational rate of the frame, but that of the particle seen from a stationary frame, is a horrible misuse of terminology that flies in the face of the whole history of classical mechanics from the rotating bucket experiment all the way to the present definition of inertial frame. (Take a look at inertial frame). It also has no meaning whatsoever in ordinary experience: if you stand or walk on a stationary carousel this r&omega;2  "fictitious force" has absolutely no effect. If you stand or walk on a rotating carousel the usual fictitious force r&Omega;2 (where &Omega; is the rotational rate of the carousel) acts upon you, and the r&omega;2 mathematical centrifugal force still has no effect upon you. If you want to predict weather patterns, the r&omega;2 centrifugal force has no role, only r&Omega;2. (Actually the Coriolis term is more important, but the same argument has a parallel for Coriolis force.)  Apparently I haven't got across the "two terminologies" idea, eh? Brews ohare (talk) 19:26, 28 September 2008 (UTC)


 * I think your view has merit, but the reliable sources use it in the way that I indicate. Fictitious forces are not only about rotating reference frames. I agree that they are not the same fictitious forces as in the rotating reference frame.- (User) Wolfkeeper (Talk) 21:13, 28 September 2008 (UTC)


 * Do you mean all "the reliable sources" or "some reliable sources"? Here's a question: suppose you walk around a stationary carousel in a circle at at angular rate &omega;.
 * Then the "inertial frame" guy will say you are subject to a centripetal inward force exerted, lets say by your sneakers upon you. There are no other forces.
 * The polar coordinate guy says your acceleration (as he calls it) is only d2r / dt2 = 0 because your radius is not changing. He explains that by saying that there is (what I will call) "phony" centrifugal force &omega;2 r, which of course, balanced the centripetal inward force resulting in zero "acceleration" d2r / dt2.
 * Now what do the two guys say to the poor student of classical mechanics who is told that Newton's laws are the same in all inertial frames (Special principle of relativity)?
 * To the inertial guy there is really only a centripetal force supporting a circular motion. That's true regardless of your choice of coordinates: describe the path in Cartesian, polar, elliptic or whatever.
 * To the coordinate guy, yeah it's an inertial frame. But just a minute: in Cartesian coordinates there is only a centripetal force. But in a polar coordinate system, there is zero net force, even though the guy is in a circular path. And in elliptical coordinates or some cockamamie set of qk coordinates? According to the coordinate guy there is some outward force opposing (but not necessarily balancing) the centripetal force, but to make d2qk / dt2 = 0, who knows what the fictitious force is? Stay tuned while I get out my differential calculus. Or better yet, tell the guy to stop walking in a circle and go in a path where d2qk / dt2 = 0; that'd make my calculations easier.
 * To the guy doing the circular walk, in a non-inertial frame where he is stationary, its pretty clear: he has to fight that centrifugal force r&omega;2 or he's going off in a straight line: don't tell me about some "phony" d2qk / dt2 = 0.
 * To Fugal: the inertial guy is nuts: he always uses Cartesian coordinates, even if he thinks he isn't. He should get a book and read up. And by the way, watch out: these authors can be tricky. Brews ohare (talk) 22:07, 28 September 2008 (UTC)
 * BTW, this discussion probably is irrelevant to Reactive centrifugal force because it is a reaction to centripetal force, and there ain't no doubt about that. Brews ohare (talk) 23:47, 28 September 2008 (UTC)

There is no such thing as reactive centrifugal force
There is no such thing as reactive centrifugal force. When an object is swung in a circle on the end of a string, the tension in the string causes an inward acting centripetal force to act. The reaction to the centripetal force is the equal and opposite centripetal force acting on the pivot.


 * It seems that by being equal and opposite to the centripetal force, the reaction cannot be centripetal, that is towards the center. But that is all beside the point. The simple fact that there is a reference, published by Princeton University Press, no less, means that at least one reliable source says that there is such a thing, and that's what is important on Wikipedia. If another, similarly reliable, published source could be found that asserts that there is no such thing as reactive centrifugal force, then we could update this article to state that "some authors say that it does not exist." -AndrewDressel (talk) 01:45, 12 April 2009 (UTC)

The tension in the string is initially caused by the outward centrifugal force. This outward centrifugal force is the same centrifugal force that appears in the radial planetary orbital equation, and which is treated in another article but without its name being mentioned. See the planetary orbital section in centrifugal force (rotating reference frame).

It is the same centrifugal force which arises in rotating frames of reference when the object in question is co-rotating with the frame.

There is only one universal centrifugal force. David Tombe (talk) 00:08, 12 April 2009 (UTC)


 * Andrew, what exactly does your one reliable source say? What are the exact words?


 * Well, it was tricky, but I clicked on the link provided, and Google Books was kind enough to highlight the relevant text in yellow. This is what it says on page 47: "Similarly, the sun will feel such a reactive, centrifugal force from each of the planets that it holds in a orbit by its force of gravity." The third reference given, Fluid Mechanics, published by PHI Learning Pvt. Ltd. in 2004, also appears to be reliable. Again, Google Books reveals the exact quotation on page 121 to be "Note that the reactive centrifugal force on the CV acts outward." -AndrewDressel (talk) 15:03, 12 April 2009 (UTC)


 * If it's just a case of needing one single reliable source, then that is a recipe for disaster, since there are so many conflicting sources. This problem needs to be analyzed rationally over a balance of sources and natural reasoning.


 * It turns out that there is more than one. Are there any that assert that "there is no such thing as reactive centrifugal force?" -AndrewDressel (talk) 15:03, 12 April 2009 (UTC)


 * On the point which you made above, the reacting centripetal force on the pivot will also be towards the centre from its own perspective.


 * If the pivot were also moving about the center 180 degrees out of phase with the object, sure, but what if it were stationary and actually at the center? At every point along the string, each segment will experience a centripetal force from the next inboard segment, and a centrifugal force from the next outboard segment. -AndrewDressel (talk) 15:03, 12 April 2009 (UTC)

Andrew, both of the two centripetal forces will act inwards towards the common centre of mass in every situation. And both of the two centrifugal forces will act outwards. We will have two sets of action-reaction pairs. In a circular motion, all four forces will be equal. But in elliptical motion, the centrifugal force and the centripetal force will not be equal in general. The centrifugal force and the centripetal force do not form an action-reaction pair, even in circular cases where they are equal in magnitude. David Tombe (talk) 21:20, 12 April 2009 (UTC)


 * The centrifugal force which appears in the planetary orbital equation is the one and only centrifugal force. Imagine that we could switch gravity off and then attach a string from the Earth to the Moon. The centrifugal force in the Kepler problem would still exist, and it is the force that would pull the string taut. Once the string had been pulled taut, the tension in the string would then serve to act as the centripetal force which would keep the Moon in orbit.


 * So as you can see, the centrifugal force is neither fictitious, nor reactive. This topic can be easily handled inside one single article. The only reason why it was split in the first place was to hide all evidence that centrifugal force might not be entirely fictitious. The misunderstood notion of reactive centrifugal force tread too dangerously on the idea that centrifugal force might be real, and so it was removed to a separate article which doesn't get first hits on google searches.David Tombe (talk) 12:44, 12 April 2009 (UTC)


 * No, it was split because the reactive centrifugal force acts on an entirely different object to the centrifugal force.- (User) Wolfkeeper (Talk) 14:42, 12 April 2009 (UTC)


 * For example in a ball bearing, reactive centrifugal force acts on the outer races, but centrifugal force acts on the balls, (and even then it only acts on the balls when viewed from a rotating reference frame.- (User) Wolfkeeper (Talk) 14:45, 12 April 2009 (UTC)

I support Wolfkeeper on this one. If time is taken to understand the comparative table at Reactive_centrifugal_force, any confusion should be resolved. Brews ohare (talk) 17:03, 12 April 2009 (UTC)


 * It's the same analogy as between weight and gravity. Gravity acts on an object. That object's weight then pushes on the ground.


 * The concept which is being described in this article is the effect which an object that is being acted on by centrifugal force, transmits to another object. Basically the concept which is being described here is to centrifugal force, what weight is to gravity. That is not a basis for having two separate articles about centrifugal force. That could all be described in a single centrifugal force article, because the centrifugal force which causes the knock on effect is the very same centrifugal force that you are describing for co-rotating objects in rotating frames in the other article. And that centrifugal force is the same centrifugal force that appears in the planetary orbit equation.


 * And the knock on effect which you are describing here is not even reactive. It is the pro-active mechanism which pulls a string taut, or which pushes on the floor of a rotating cylinder so as to induce the tension in the string or the normal reaction. It is the centripetal force that is reacting in these situations. Not only are you wrong to split the article, but you have also got cause and effect the wrong way around. David Tombe (talk) 21:15, 12 April 2009 (UTC)

This viewpoint that everything should be done in one article is a mistake. Both articles are necessary. Read the comparative table at Reactive_centrifugal_force. Brews ohare (talk) 04:20, 13 April 2009 (UTC)


 * Andrew and Brews, Yes there are indeed references which use the term 'reactive centrifugal force'. But these refer to the one and only centrifugal force.


 * Consider this all inclusive example. Two objects move with mutual transverse speed. There will be a gravitational force and a centrifugal force as per the planetary orbital equation. If the gravitational force is very weak, then the orbit will be a hyperbola.


 * Now attach a string between the two objects. The centrifugal force acting on the two objects will then pull on the string. It is this latter effect which is covered by this article. The pulling effect on the string will make the string go taut and introduce a tension. This tension will give rise to an inward centripetal force which is greater than the gravity, and the orbit will become circular.


 * That is the entire topic of centrifugal force in a nutshell. We cannot have two articles just to cater for (1) the centrifugal force on the objects, and (2) The centrifugal force which the objects then transmit to the string. David Tombe (talk) 11:59, 13 April 2009 (UTC)

The recent edits
Wolfkeeper, your tidying up of that last line in the introduction was actually OK. It is in line with my own edit on the issue. But there wasn't really any need for the re-wording, although I know that you were undoing what Dick undid.

Nevertheless, there was no need to then erase my history article. Dick erased it first and it was in effect an act of spiteful vandalism. The contents of that edit were straight out of the supplied source, and the notorious dispute between Leibniz and Newton and its relation to the history of centrifugal force is very relevant for this article, especially since you are the one that insists that the Newtonian interpration be given a special page of its own. David Tombe (talk) 12:56, 3 May 2009 (UTC)


 * Oh, come on, David -- spiteful vandalism? If you had even one other editor backing your idiosyncratic point of view we might have something to discuss, but for you to try to use Newton and Leibniz as a vehicle to push your strange understanding of physics is just not something we're likely to allow here. Dicklyon (talk) 18:30, 3 May 2009 (UTC)

Dick, That's correct. There has been nobody else but myself in the last two years who has advocated the approach that was adopted by Leibniz and Goldstein. It is not my approach. I didn't invent it. I did the classical mechanics course many years ago and it dealt with planetary orbits as per Goldstein. Centrifugal force is independent of centripetal force and in the case of when gravity is the centripetal force, the two operate in tandem to yield hyperbolic, parabolic, or elliptical orbits.

You are one of the few who has actually followed up Goldstein and who appears to have comprehended the Leibniz approach. But you are now behaving as badly as Isaac Newton in that you are trying to mask Leibniz's approach. But unlike Newton, you are trying to get it all tangled up with fictitious forces and rotating frames of reference when there is no need to do so. Newton on the other hand messed it all up by making a general equality between centrifugal force and centripetal force and calling them an action-reaction pair as per his 3rd law of motion.

I'm going to go back to the talk page on the other article and list the different approaches to what is essentially one topic. David Tombe (talk) 18:41, 3 May 2009 (UTC)

There is no such thing as reactive centrifugal force (again)
This sentence in the first paragraph: "This reactive force is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration." is not generally true. It is certainly not true in the case of two bodies in gravitational orbit about each other. In that case there are only two forces: the gravitational forces of each body on the other. Both forces are centripetal. Each body exerts a force on the other causing the other to accelerate centripetally, ie. toward the centre of rotation, which is the centre of mass of the two body system.

The reference is to Delo E. Mook & Thomas Vargish (1987). Inside relativity. Princeton NJ: Princeton University Press. p. p. 47. Unfortunately, this reference is wrong in attributing the force of the earth on the sun as being a centrifugal force. The force of gravity of the earth on the sun, causes the sun to accelerate toward the centre of rotation, which is the centre of mass of the earth/sun system, so it is centripetal. -AMSask (talk) 19:04, 15 September 2011 (UTC)


 * I agree that gravitational attraction seems to be a situation in which the reactive centrifugal force as described in this article isn't really centrifugal. As the moon orbits the earth, it does pull on the earth, but towards their common Barycenter, not away from it. Yes, the reference seems to provide a poor example. Perhaps we should narrow the definition, if we can find a better reference.


 * I believe it is incorrect, however, to describe the gravitational attraction between two bodies as two forces. Instead, the bodies are pulled towards each other by opposite ends of the same force, as described by Newton's third law. -AndrewDressel (talk) 19:25, 15 September 2011 (UTC)


 * ??Opposite ends of the same force? You can have opposite ends of a rope with tension. But gravitational force does not have "ends". The bodies simply exert equal and opposite attractive forces on each other at a distance.  That is what Newton's Law of Universal Gravitation says. Both bodies experience acceleration so both bodies have forces acting on them, the force on one being equal and opposite to the force on the other. AMSask (talk) 04:00, 17 September 2011 (UTC)


 * I don't see where Newton's Third Law is limited to ropes or any other type of force; it applies to all forces. Hellingman explains that all forces are interactions between different bodies, and there is no such thing as a unidirectional force or a force that acts on only one body.(C Hellingman (1992). "Newton’s third law revisited". Phys. Educ. 27 (2): 112–115.) Thus, the ends of a gravitational force are the two masses that attract each other. -AndrewDressel (talk) 13:26, 17 September 2011 (UTC)


 * It is undeniable that forces come in pairs. So I am confused by what you meant then by: "I believe it is incorrect, however, to describe the gravitational attraction between two bodies as two forces." In the sun-earth system, there is the force of the sun on the earth and the force of the earth on the sun. Those are two forces because they operate on two distinct bodies and cause two distinct accelerations. I have not heard this terminology before about the "ends" of a force. AMSask (talk) 15:24, 18 September 2011 (UTC)


 * It is completely deniable that forces come in pairs. Even Newton did it, as Hellingman points out:
 * "In the end of the third book of the Principia we find the following passage, wherein Newton explains why the forces celestial bodies exert on each other are proportional to the masses of both bodies. In Cajori’s (1966) translation:"
 * "For all action is mutual, and makes the bodies approach one to the other, and therefore must be the same in both bodies. It is true that we may consider one body as attracting, another as attracted; but this distinction is more mathematical than natural. . . . It is not one action by which the Sun attracts Jupiter, and another by which Jupiter attracts the Sun; but it is one action by which the Sun and Jupiter mutually endeavour to come nearer together (by the third Law of Motion); and by the action with which Jupiter attracts the Sun. Likewise Jupiter and the Sun endeavour to come nearer together. But the Sun is not attracted towards Jupiter by a twofold action, nor Jupiter by a twofold action towards the Sun; but it is one single intermediate action, by which both approach nearer together." (emphasis mine)
 * "One single intermediate action! One can almost hear the word interaction, much in use nowadays." (emphasis Hellingman's)
 * Hellingman continues by explaining why this seemingly trivial distinction is important:
 * "Interpreting forces as sides of a single interaction implies a very important shift of focus of attention. The attention is drawn away from the objects themselves to ‘somewhere’ between the objects. Failure to see the ‘between’-like character of a force lies at the bottom of all misconceptions."
 * -AndrewDressel (talk) 06:44, 19 September 2011


 * There are many different ways of mentally picturing or modeling the concept of force. But one cannot deny that in a two body interaction there are two distinct bodies (masses) and each have distinct rates of change of momentum. So, unless you redefine force as something other than dp/dt, there are two forces. AMSask (talk) 21:33, 18 September 2011 (UTC)


 * I am not sure what you mean by "distinct". If you mean "different", then by saying "each have distinct rates of change of momentum", it sounds as if you are saying that dp/dt of one mass does not equal dp/dt of the second mass. If force is defined as dp/dt, then it seems that you would be saying that the force that acts on one mass is not equal in magnitude to the force that acts on the second mass, and that would contract Newton's Third Law, independent of whether we consider the force between two objects as a single force or two separate forces. Instead, if by "distinct" you mean perhaps "equal but separate", then I cannot understand how you conclude that there must be two forces. I see no reason why a single force cannot change the momentum of two different particles equally, just as the tension in a single rope or spring would if either where attached to both of the particles. -AndrewDressel (talk) 01:56, 19 September 2011 (UTC)


 * The magnitudes of the two forces are equal. But they operate on two different bodies and in two different directions. So the forces can be readily distinguished. The reason there are two different forces is because force is defined as the time rate of change of a body's momentum vector as measured in an inertial frame of reference. If you want to use a different definition of force, you will have to be clear how you define it and you should probably call it something else. AMSask (talk) 04:13, 19 September 2011 (UTC)


 * I think now I see your point. Newton took care to explain that gravitational attraction "is one action by which the Sun and Jupiter mutually endeavour to come nearer together", but perhaps for the sake of calculation, the preferred current convention is to think of a single force as the change in momentum of only one distinguishable mass at a time. Perhaps I must retract my assertion that "it is incorrect to describe the gravitational attraction between two bodies as two forces" and leave you to wrestle with Dicklyon about what to call them. -AndrewDressel (talk) 12:56, 19 September 2011 (UTC)


 * It is not a "preferred current convention" to think of a single force as the change in momentum of only one distinguishable mass at a time. It is the very essence of the meaning of "force". Similarly, we don't say it is a "preferred current convention" to speak of a body's acceleration as the rate of change of its velocity. AMSask (talk) 16:22, 19 September 2011 (UTC)


 * I think I may have spoken too soon. If force is strictly defined as dp/dt, then what of forces that do not cause a change in momentum of an object? Must they be zero or not be forces? My mechanics textbook even begins with "force can be defined by the amount of spring stretch it causes." At the same time, if force is defined as dp/dt, are we to assume that it has only one end and changes the momentum of only one object at a time? No, I don't see where it is written that the very essence of the meaning of "force" is the change in momentum of only one distinguishable mass at a time. Instead, it is often written that force can be defined as dp/dt, but by Newton's third law, we know that it must change the momentum of two objects at the same time, unless additional forces are applied simultaneously to the second object. -AndrewDressel (talk) 17:13, 19 September 2011 (UTC)


 * You can say that the interaction of two bodies causes the momentum of the two bodies to change at the same time. You can say that the interaction causes each body to exert a force on the other body that is equal and opposite to the force that is exerted on it by the other. Those forces cause the changes in momentum that result from the interaction. But if you are saying that it is a (single) force that changes the momentum of the two bodies at the same time, this would not be correct.AMSask (talk) 03:17, 20 September 2011 (UTC)


 * Where is this written? I cannot find it in the Principia, my mechanics textbook, or a peer-reviewed journal. Where have you found it? -AndrewDressel (talk) 13:02, 20 September 2011 (UTC)


 * You will have to read your textbooks more carefully. Here is an example of the kind of problem discussed in virtually every introductory textbook on physics: Consider a 10 kg block moving at 1 m/sec colliding simultaneously with a 1 kg block and a 2 kg block on a frictionless surface. The collision lasts .01 second. Calculate the (average) forces that arise in this collision. The answer is not: "There is only one force". If you disagree, I would be very interested in your answer for the value and direction of that force. There are three objects and each object experiences a different change in momentum. At any given moment there is a different force on each of the three blocks.


 * You should be careful about how you use the "it is not found in any physics text" argument. You will not find any discussion of "reactive centrifugal force" in a physics textbook because no one uses the term. It is at best a poor and misleading term, and in the example given by Mook and Vargish in their book it is quite wrong, for the reasons I have given.AMSask (talk) 19:11, 20 September 2011 (UTC)


 * In the case of the reactive force of the Earth on the Sun, the direction of the force is toward the Earth. From the point of view of the Sun relative to the center of the system, this is centripetal (or nearly so, so non-circular orbit), but that's not what reactive centrifugal force is referring to.  It's the force that an object in circular motion exerts back on the object providing its centripetal force; it's in the opposite direction of the centripetal force; from the point of view of this object moving in a circle, it's centrifugal, away from the center of its osculating circle.  Yes, it may be an awkward deprecated concept, but it's not nearly as bad as what you'll have if you start calling it sometimes centripetal. Dicklyon (talk) 16:00, 17 September 2011 (UTC)


 * There are two distinct forces in a two body gravitational interaction. Both arise from a single gravitational interaction. There is the force on the sun by the earth that results in a centripetal acceleration of the sun toward the earth-sun centre of mass. And there is the force on the earth by the sun, which also results in a centripetal acceleration of the earth toward the same point. If we define force = dp/dt then there are two forces. If you define force as the interaction, then you end up with a completely different definition of force. Before you can talk about the "force" as being the interaction you have to define what you mean: how does it relate to dp/dt?


 * In a two-body interaction, each force can be considered an action force or a reaction force. Action and reaction are poor terms to use because it suggests that the "reaction" force arises after or in response to the "action" force - ie. that they are not simultaneous. The conservation of momentum, which appears to be an inviolable principle in all physics, depends on both forces applying simultaneously.AMSask (talk) 21:33, 18 September 2011 (UTC)


 * If you want to fix the sentence in question, change it to "This reactive force is directed away from the center of rotation of the rotating mass, and is exerted by the rotating mass on the object that originates the centripetal acceleration." Or, since "away from the center" is not a direction at all, you can put "This reactive force is directed from the center of rotation of the rotating mass toward the rotating mass, and is exerted by the rotating mass on the object that originates the centripetal acceleration." Dicklyon (talk) 16:00, 17 September 2011 (UTC)


 * But that would be completely wrong. In a two body interaction involving rotation there are only two forces. Each body exerts a force on the other. There are only two bodies that accelerate: both accelerate toward the centre of rotation. If you draw the second time derivative of the radial displacement vector of the centre of mass of each body, the direction of that vector will be opposite to the direction of the radial displacement vector of that body. If you multiply that acceleration vector by the body's mass, that is the definition of a centripetal force. There is no acceleration that is in the same direction as the radial displacement vector of the accelerating body. AMSask (talk) 21:33, 18 September 2011 (UTC)


 * I have reviewed the Mook book, and I don't see anything wrong there; it does not claim that the directions of the reactive centrifugal forces on the Sun are anything but toward the planets. And with all those planets jerking the Sun around, the motion is not anything like circular about a center anyway, so you certainly can't be right to suggest that the force is centripetal. Dicklyon (talk) 16:00, 17 September 2011 (UTC)


 * First of all, the direction of a (net) force on a body is the direction of the acceleration of that body. $$\vec{F} = \frac{d\vec{p}}{dt} = m\vec{a}$$. Whether the orbit is elliptical, circular, parabolic or hyperbolic, the acceleration, hence force, is always centripetal (opposite to the body's radial displacement from the centre of rotation). The sun only accelerates toward the earth in the non-inertial frame of reference of the earth. In an inertial frame of reference, both the sun and the earth accelerate toward the centre of mass of the sun-earth system (assuming there are no other planets).AMSask (talk) 21:33, 18 September 2011 (UTC)


 * Here's another book (old) about the concept; not very clear about what the force is exerted on, but clear about the direction being opposite to the centripetal. Here is a newer book.  and here is a 1905 Science mag discussion this concept in books, and they think it's a bad idea that should be retired (a discussion still going on today, though it has mostly been done).  One of the books they're reviewing is here; it's clear what direction is meant by centrifugal, as it's with respect to the body's center of curvature of motion, nothing to do with the body that the force is acting on.  Dicklyon (talk) 16:00, 17 September 2011 (UTC)
 * Dragging up books from 1905 is not the way to write a WP article. Of course, you can call any force acting away from any instantaneous centre of rotation a centrifugal force but this serves no useful purpose and is very confusing to many people.  This usage has been completely dropped by modern engineers, physicists, and mathematicians and has no place here except in a historical context. Martin Hogbin (talk) 09:55, 13 March 2012 (UTC)

There is no such thing as reactive centrifugal force (yet again) -- Article really should be deleted
The central premise of this article is: "Centrifugal force is an actual force as it is the 'equal and opposite reaction' of the centripetal force -- and that is another perfectly valid way of looking at it." That is a very very common misunderstanding, but it is a misunderstanding. It is not a valid way of looking at it.

To be short and sweet about why: It's a misinterpretation of "F=ma". Just because the vector "ma" is equal to the vector of the net force (F), doesn't mean that "ma" is a force. In some disciplines, it has been useful to write it as "F-ma=0" which further makes "ma" look like a force. This suggests that the sum of forces on anything is always zero (which is incorrect). The thinking goes that since the centripetal force is real (which is correct) then to make the sum of forces zero, the centrifugal force must be it's "equal and opposite reaction" to balance off the real centripetal force. Right? Nope, that is not true because the sum of forces (net force) doesn't need to be zero. The article is also a big misinterpretation of Newton's third law. But, I don't want to belabor an explanation as to why the premise is so incorrect. I could, but I will spare you. The community of solidly-founded physics professionals will support me on this.

Besides the bad premise, the article also is almost entirely unreferenced. The single reference appears to be about relativity while the article is about classical mechanics. The example in it also has reliability issues (remarked in previous discussions). This shortness of references is most assuredly due to the difficulty of coming up with reliable references in support. The article is basically WP:OR.

The article mentions a bunch of uses and examples of centrifugal force. These are all immaterial and off-topic to the main (extraordinary and dubious) claim that centrifugal force is something other than the inertial opposition to an accelerating frame (which is itself the result of non-zero net force). Ignoring that frippery, the article contains very little on-topic heft. That remaining on-topic material should be deleted not merely for its dubiousity and uncitability, but for it's outright wrongness. In short, the whole article really should be deleted.

User276 (talk) 08:09, 24 July 2012 (UTC)


 * You, or anyone else, can nominate it at Articles for Deletion, if you wish. Then, other users will discuss whether or not they support your nomination. Based on the comments made by other editors and the arguments in those comments, an administrator will close the discussion in 7 days or so (more, if required) and, if the community consensus is to delete the page, it will be deleted. dalahäst (let's talk!) 08:14, 24 July 2012 (UTC)


 * User276, it's clear to all that the old concept of reactive centrifugal force is not a preferred way of looking at things these days, and is not what is usually meant by centrifugal force (rotating reference frame). That's why we have the summary-style article centrifugal force to contrast them.  But I don't understand your "no such thing" comment.  Cannot the force of the moving object on the object that is putting a force on it be called the reactive centrifugal force?  It does seem to be called that by some (more in older sources).  I add a few more refs.  Dicklyon (talk) 07:41, 25 July 2012 (UTC)

Hi Dicklyon, et al,

Questions in science aren't resolved by opinions about whether a concept is old or new or preferred or not preferred, right? They are, of course, resolved among scientists with regard to reliability, i.e. how well they predict experimental results. However, maybe questions in WP includeability are? Or aren't? Anyway, we do know that reliable references are required. That seems straightforward enough, except how do we know what references are reliable? Here, it is up to the editors' knowledge and judgment to make that distinction. It is also sometimes necessary to make reasoned arguments as to what refs are reliable by arguing about the actual science. I am arguing here that any ref that asserts "reactive" CF is not reliable.

Like you said, the refs calling it "reactive" tend to be older. That makes sense because science is all about casting off unreliable or less reliable ideas about the nature of nature. Science does this all the time. Science is a continuous improvement process. Sometimes, modern writers look to the old refs and repeat their errors. That, along with actual misunderstanding on the modern writers' part, is what is behind the modern refs' usage of "reactive". I guarantee though, that among modern PhD physicists, you won't find one who asserts the "reactive" explanation. We must consider all "reactive" refs to be unreliable.

Some of the factors that lead to confusion are:

1) The very unfortunate term "fictitious" force. There are better terms that don't connote unreality.  The "fictitious" force is a real "thing", it's just not produced by the Fundamental Forces in the Standard Model.  The thing called "fictious" is just the "ma" part of F=ma (or F-ma=0).  Still real, just not a fundamental force.

2) The fact that there are force pairs all over the place in a circling-weight-on-a-string system and in the myriad other examples of CF. It is easy to confuse these force pairs with the actual "source" of CF.

3) There is a lack of discernment in the use of the word "reactive". The general meaning that something happens "in turn" and "in response" to something else is muddled into the more specific meaning here: "that centrifugal force is an actual force as it is the 'equal and opposite reaction' of the centripetal force -- and that is another perfectly valid way of looking at it."  This specific meaning is always wrong.  The general meaning can be right, but intermingling it with the specific meaning can incorrectly make the specific meaning look correct when it is not.

If the idea that centrifugal force is "an actual force as it is the 'equal and opposite reaction' of the centripetal force" is included, it should be in a historical context or in a "Common Misconceptions" section of the main (and single) article. There it can be pointed out exactly why it is a superseded concept.

User276 (talk) 17:31, 9 August 2012 (UTC)


 * The fact that it has largely been supplanted as the preferred concept doesn't mean it doesn't exist as a real force. Don't we already discuss this in the history of the conception of CF?  I linked that in the lead.  Dicklyon (talk) 17:42, 9 August 2012 (UTC)

True, the fact that it has largely been supplanted as the preferred concept doesn't mean CF doesn't exist as a real force. But, the fact that CF doesn't exist as a real force is true independently! :-) But all this really depends on what a "real" force is of course.  Calling it a "real" force implies that it is one of the fundamental forces in the standard model.  That's the modern usage of "real force" among the most reliable practitioners (Physics PhD's, etc.).  So, in this definition of "real" force, CF most assuredly does not exist as a "real" force.  Although, CF is indeed a real "thing", just not a "real" force.  The real thing that it is is the "ma" part of "F=ma" (the sum of all "real" forces = ma)

The idea that CF is a "real" force and that it is just the "equal and opposite" to the centripetal force belongs in the dustbin of "Common Misconceptions" in the main article only and nowhere else. People buy into it in the modern day mostly because of "confusion number 2" above. They don't do a full and correct analysis of the forces and their reactions (the "general" sense - beware "confusion number 3").

User276 (talk) 18:48, 9 August 2012 (UTC)


 * I don't understand or agree with Calling it a "real" force implies that it is one of the fundamental forces in the standard model. Do you have a source for this concept of "real force"?  Dicklyon (talk) 18:53, 9 August 2012 (UTC)

Source? How about Standard Model or Beyond the Standard Model? When I was a kid in the '70s, the (four) forces were Electromagnetic, Strong, Weak, and Gravitational. Now that Electromagnetic has been tied to Weak, it's called "Electroweak". All these forces are carried by particles. For example, in the case of the Electromagnetic forces that particle is the photon. All forces, chemical bonds, etc. - everything that can "push" on something else is done via particles carrying these forces. In some cases like gravity, experimental evidence is thin, but the point is that these are the only "real" (non-"fictitious") forces. These are the things that sum up to go into the "F" side of "F=ma". The "ma" side is the resulting acceleration. I don't like the term "fictitious" either (see "confusion number 1" above). Like I said, a "fictitious force" is a real "thing", just not a "real" (or non fictitious) force. I only use the term "real" as the opposite of that awful term "fictitious" as much as I dislike how they incidentally (and incorrectly) imply existence or non existence.

User276 (talk) 20:18, 9 August 2012 (UTC)

String-Ball-Post diagram concept is so incredibly wrong...
The diagram (and whole article) purports that the "equal and opposite" of the centripetal force (CPF) is the centrifugal force (CFF). But the CPF's "opposite" (the force keeping the end/center of the string from accelerating) is actually the force on the post. The post exerts a force on the string and the string exerts a force on the post.

The post would move if the only force on it was the string. What really happens is the post puts a force on the earth and the earth accelerates accordingly inversely proportional to its mass, which of course makes the post appear fixed (a mistaken idea leading to all kinds of misconceptions). On the other end, the post puts a force on the string, the string puts a force on the ball, and the ball accelerates inversely proportional to its mass. The system is really two "fictitious forces" ("mA" and "Ma") connected by "real" (standard model) forces (string-post-earth) resulting in zero net acceleration.

The diagram is a major error in concept and it supports a major error, which is the whole article. The article must either be (1) deleted, or (2) at a bare minimum it should change its perspective from asserting this as a valid description to instead demonstrating an example of an invalid description, why it's invalid, and its history.

User276 (talk) 19:49, 9 August 2012 (UTC)


 * I'm not following you on what's invalid about it. Can you find a source that explains why the concept of reactive centrifugal force is invalid?  Dicklyon (talk) 20:18, 9 August 2012 (UTC)

Take a look as "Confusion number 3" in the previous section regarding "reactive", we all really need to be more specific.

All this is indeed a hard nut to grasp. I'm an engineer and I really only started to understand it a few years ago when I started discussing it with a physics professor friend. I started out believing this "reactive" perspective too, but it just doesn't hold up. The "fictitious force" model is indeed harder to grasp, but that's no reason to be attracted to a simpler, but wrong, model and then call it "equally valid".

You are defending an article that essentially says "The sun goes around the earth" and you want sources saying otherwise? Sources abound! Why don't you go get those sources? You'd learn something in the process. If instead you want to only seek out sources that support validity, you can find them. But, like I said, reliability of sources can only be estimated by applying the expertise of editors. And, editors who actually know their stuff know that any source asserting validity is not reliable. I've made arguments regarding the invalidity of the article as have many others before me.

The article amounts to scientific quackery as it stands and I can't spend any more of my time educating you or anyone as to why it is. Please review the explanations here and in the above sections, and/or go out and educate yourself some more on the matter. I will be making "bold" edits soon to correct some of the most egregious problems if someone doesn't pipe up and get to it first.

User276 (talk) 21:11, 9 August 2012 (UTC)