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[edit] Applications

I don't think the "applications" section should be here. All of the examples appear to have a closer connection to the fictitious force. Though they commonly also involve a reactive centrifugal force, it is either incidental or secondary to the mechanism being described. –Henning Makholm 03:00, 27 April 2008 (UTC)

[edit] 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)

[edit] 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: [1] [2] [3] [4] [5]. 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)