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Comparison table

I enthusiastically oppose any attempt to combine the centrifugal force article with the reactive centrifugal force article. They are not aspects of the same thing, as the examples in the two articles clearly demonstrate and as the table below makes abundantly clear:

The bottom row of entries in the table are particularly telling.Brews ohare (talk) 20:47, 25 April 2009 (UTC)

The table looks reasonably sensible. Why not include it in an article on centrifugal force to help clarify the distinction between the two views? Dicklyon (talk) 20:59, 25 April 2009 (UTC)

The only distinction between the two aspects is that one is the centrifugal force which acts on an object as per the term in the radial planetary orbital equation. The other is the effect which that object then transmits to another object on contact. They can both be treated within the context of a rotating frame of reference if you feel you need to insert a frame of reference around the situation. But you don't have to involve a rotating frame of reference. It is quite voluntary. Centrifugal force is one subject. There is no need for two articles in wikipedia. David Tombe (talk) 00:07, 26 April 2009 (UTC)

It's not a matter of "on contact"; contact has nothing to do with it. And the "fictious centrifugal force" is zero in an inertial frame, so what you're saying isn't consistent with physics as we know it. But I agree there's no need for two articles. Dicklyon (talk) 02:24, 26 April 2009 (UTC)

Brews, the table doesn't clearly demonstrate that they are not aspects of the same thing. Let's take one example. It states that the so-called reactive centrifugal force applies in any frame of reference. That is true. And what is it reacting to? It certainly isn't reacting to the centripetal force because the centripetal force doesn't come into existence until the other centrifugal force, as per the planetary orbital equation, causes either a tension or a pressure. You are saying that the latter is a fictitious force that is only observable in rotating frames of reference? Yet the latter (fictitious force) is the very thing which causes the former (reactive) effect which the table says can apply in any frame of reference? David Tombe (talk) 00:17, 26 April 2009 (UTC)

It's the reaction to the centripetal force, which has to be there to cause the object to move in a curved path. The force of the string makes the ball's path curve, and the reaction force from the ball's acceleration keeps the string under tension. Some authors prefer to use the term "inertial force", but sometimes mix up whether they mean the force on the object the makes it curve or the force on the string, or both (they're equal when the path is circular). Dicklyon (talk) 02:24, 26 April 2009 (UTC)

Dick, what makes the string go taut in the first place? There is no centripetal force (apart from the negligible gravity) until the string goes taut. So what makes the string go taut in the first place? It's the centrifugal force as per the planetary orbital equation. So clearly, the centrifugal force cannot be a reaction to the centripetal force.

Equation 3-11 in Goldstein,

${\displaystyle m{\ddot {r}}-mr{\dot {\theta }}^{2}=f(r)}$

applies for any centripetal force. It doesn't matter whether the centripetal force, ${\displaystyle f(r)}$, is (1) gravity, (2) tension in a string, or (3) both. The centrifugal force term is an independent term which is not necessarily equal to the centripetal force term. Hence, the centrifugal force cannot be a reaction to the centripetal force in any circumstances whatsoever. David Tombe (talk) 12:26, 26 April 2009 (UTC)

David, for your first query, what makes the strings go taut, that depends on the setup; for example, if you have a limp string, starting with the ball inside the circle (defined by radius equal to string length) and moving in a straight line, the ball will at some point reach the circle, where the string will tighten and provide whatever force is needed to keep the ball from exiting the circle.

On your second point, it's very true. The centrifugal force that Goldstein defines in the 1D problem (distance r) is not equal to the reactive centrifugal force except in the case of circular motion, where that net f(r) is zero. Dicklyon (talk) 14:51, 26 April 2009 (UTC)

Dick, Yes. So it is the outward centrifugal force which makes the string go taut. The centripetal force doesn't come about until the string is taut. And yes, the centrifugal force is only equal to the centripetal force in the special case of circular motion. Whoever drew up that comparison table was trying too hard to make a case for two different centrifugal forces.

But there are two different centrifugal forces in use here; the fictitious force of the rotating system and the reaction force to centripetal force. When you say "The centripetal force doesn't come about until the string is taut,", that's also true of the reaction force, the force the ball exerts on the string. It's not true of the fictitious centrifugal force that you see in the co-rotating system even while the ball is moving in a straight line with slack string. They're just different things, which is why Brews argues they should have separate articles. But of course, they are also closely related, as in equal for the case of circular motion. Dicklyon (talk) 19:22, 26 April 2009 (UTC)

The most common argument that they put forward for having two different centrifugal forces is that the two centrifugal forces act on different bodies. Yes. Centrifugal force acts on body A. Body A contacts body B and transmits the effect. It's a very sophomoric argument and it's hardly a basis for two wikipedia pages. But I know that you, like myself, have been advocating a unified article, and I noted that you also stated that two aspects of the same overall effect is not a basis for having two pages on wikipedia.

Again, contact has nothing to do with it. There are two different conceptions of centrifugal force, they act on different bodies, and they have different values, and one is "fictitious" in the sense that it doesn't exist in an inertial frame. It's not an unreasonable argument for different articles, nonetheless I agree that one article could cover the relationship better. Dicklyon (talk) 19:22, 26 April 2009 (UTC)

No. They both have the same value and the transmission of the effect from A to B can only be by contact. David Tombe (talk) 19:39, 26 April 2009 (UTC)

When we get a unified article, it will be easier to discuss the problem in its entirety. Two balls connected by a string involves every single aspect of the problem. It involves gravity, albeit negligible, but that allows us to contemplate the hyperbolic orbit. Then we add the string. The outward centrifugal force pulls the string taut. The induced tension in the string then augments the inward gravity force and converts the orbit to circular.

Yes, we could cover that. But we'd need to get you to accept that "the outward centrifugal force" of a ball moving in a straight line with a slack string attached is a fiction induced by a viewpoint (a rotating viewpoint from where the other end of the string in anchored, perhaps); there's no actual force acting on anything in that case, as should be crystal clear as the ball is moving a straight line (neglecting gravity). Dicklyon (talk) 19:22, 26 April 2009 (UTC)

How can it be a fiction if it pulls the string taut? David Tombe (talk) 19:43, 26 April 2009 (UTC)

What is it doing before the string pulls the ball into a curved path? Dicklyon (talk) 20:04, 26 April 2009 (UTC)

It's not truly fictitious. The force is real, but doesn't exist in the inertial reference frame. This is usually called a 'pseudoforce'. Gravity is also a pseudoforce; and if you are in an inertial reference frame, you feel no acceleration due to gravity either.- (User) Wolfkeeper (Talk) 20:22, 26 April 2009 (UTC)

This "real" versus "fictitious" thing is vacuous without definitions; fictitious is defined the same as pseudo as you use it; I'm not certain which one is more common, but both are commonly used for these forces that do not exist in an inertial frame, but rather come up in applying f = ma in a non-inertial frame. I'm not at all sure what "real" is supposed to mean here; it's all real in the defined sense. As to which way to treat gravity, that depends on whether you mean inertial in the classical or the general relativity sense, doesn't it? I think we're pretty much stick to classical here, so gravity would not be treated as a fictitious force, but rather as a force that's felt even in an inertial frame. Dicklyon (talk) 20:34, 26 April 2009 (UTC)

The word 'fictitious' means that something is completely and utterly made up; Sherlock Holmes is fictitious; but centrifugal force/effect have real measurable consequences; so the term 'pseudo-force' is accurate whereas fictitious force is a misnomer.- (User) Wolfkeeper (Talk) 22:03, 26 April 2009 (UTC)

If that's what it means, that maybe explains David's reluctance to accept it; perhaps it's unfortunate that this fairly standard terminology is a misnomer, as you call it, but since it's what's used in the field, we should use it, too; of course, we can say it's the same as pseudoforce, and use that preferentially if that helps. It doesn't change the meaning, but may change the negative reactions to it. Dicklyon (talk) 22:36, 26 April 2009 (UTC)

I can see that you clearly understand the issues. It's only a matter of fitting a coherent and simplified article around the references. David Tombe (talk) 19:04, 26 April 2009 (UTC)

Indeed. Dicklyon (talk) 19:22, 26 April 2009 (UTC)

Dick, I'll have to retract that now since it looks like you don't understand the issues after all. Let's concentrate on the bit when the string is being pulled taut. (See section 9 in the reference which I have just supplied). What is pulling the string taut? David Tombe (talk) 19:36, 26 April 2009 (UTC)

I don't see the reference you refer to; can you repeat it? You're going elliptical on me again... Dicklyon (talk) 20:04, 26 April 2009 (UTC)

Dick, see section 9 in reference 23 on the main page. It's the reference that I inserted today.

For the record, that's this book, pp. 78–80 or so. That all looks reasonable to me. The centrifugal force (an "apparent force" in the rotating frame, as opposed to "true forces" in inertial frames, as this book calls them) is obviously pulling the string taut, when you look in the co-rotating frame; in the inertial frame, the it's the reaction to the force with which the string is accelerating the balls. Dicklyon (talk) 23:14, 26 April 2009 (UTC)

The centrifugal pseudoforce that appears in the equations of motion when you transform them to a rotating reference frame pulls it taut!!!!!!! Do you think we made this term up? If it's in the equation of motion, is it really fictitious? No! It's real physics.- (User) Wolfkeeper (Talk) 20:22, 26 April 2009 (UTC)

The other way to look at it, viewing in the inertial frame, is that the string is pulling against the inertia of the ball; when the string puts a force on the ball to move it in a circle, the string is pulled by the reaction to that force; in this view, the centrifugal force is the string tension, which exists only after the string comes tight, and it's equal to the centripetal force even if the string is stretchy. In the pseudoforce view, the centrifugal force is on the ball, even before the string is tight, and is not equal to, but often close to in balance with, the centripetal force; if the string is stretchy and the ball's radius is accelerating, they're not quite in balance; if the string's not tight yet, they're way out of balance, but the centrifugal force on the ball still exists while the ball is moving in a straight line, which is why its r is accelerating outward. Dicklyon (talk) 20:34, 26 April 2009 (UTC)

You can certainly look at the same thing, either as inertia in a newtonian centre of mass frame, or as a pseudoforce in the rotating frame. But calling one 'real' and the other 'fictitious' confuses a lot of people like David Tombe, because you're using English words incorrectly. They ask 'If it's fictitious how can it change anything in the rotating reference frame?'; which is a good question; if it actually was fictitious it couldn't. But it's not, it's a misnomer.- (User) Wolfkeeper (Talk) 23:29, 26 April 2009 (UTC)

Dick, it strikes me that you are trying too hard to not see the centrifugal force. Let's go back to the stage where the string is still slack. We will have an outward centrifugal force acting on the ball, as per equation 3-11 in Goldstein. Wolfkeeper calls it a pseudo-force and acknowledges that it is real. So we are making progress. Eventually this centrifugal force pulls on the string and makes the string go taut. This induces a tension in the string. That tension then causes an inward centripetal force to act, and the orbit gets pulled into a circle.

Where do you see two centrifugal forces in this scenario? And how do you reason that one of them is present in all frames of reference whereas the other is only present in a rotating frame of reference? And how do you reason that one of the centrifugal forces is reacting to anything? David Tombe (talk) 22:55, 26 April 2009 (UTC)

I see the centrifugal force just fine, thanks; just like Wolfkeeper I see the "apparent" or "pseudo" or "fictitious" force; calling it "real" has no obvious meaning to me; I think we all agree it's proportional to the theta-dot of the frame, whereas the force on the string doesn't depend on the rotation rate of your frame of reference. See Brews's table. Dicklyon (talk) 23:14, 26 April 2009 (UTC)

Dick, That's good that you can see the centrifugal force as per equation 3-11 in Goldstein. So who said anything about a rotating frame of reference? And where did you read in Goldstein that this force is either "apparent", "fictitious", or "pseudo"? This force can pull a string taut. And you are quite wrong when you say that the force on the string doesn't depend on the rotation rate. The force on the string, and the force in equation 3-11 are one and the same force, and that force does depend on the rotation rate. David Tombe (talk) 23:22, 26 April 2009 (UTC)

Goldstein uses the word "fictitious" for the co-rotating 1D system, though not explicitly for the force; but it's same as what others call those things. If you look at the ball moving in a straight line in an inertial frame, it's obviously unaccelerated and therefore has no force on it; only when you rotate to face it and measure r do you see an apparent acceleration away from you. I suppose I can repeat this a few more times for those of you who have a mention block about it. Dicklyon (talk) 23:32, 26 April 2009 (UTC)

Dick, Goldstein states that equation 3-12 is the same equation as occurs in the equivalent fictitious 1-D problem. He does not say that either equation 3-12 or equation 3-11 is a fictitious 1-D equation. Indeed, equation 3-11 which contains the centrifugal force in its familiar form cannot possibly be a 1-D equation because of the angular velocity term. You have totally misrepresented Goldstein on this point and you have done it opportunistically and repeatedly. You have played on simplistic word association. You have seen the word 'fictitious' in a completely different context and you have opportunistically swooped in and milked it dry.

And now you are ducking the main point again. We know that there is a centrifugal force acting on the ball even before the string becomes taut. That centrifugal force eventually pulls the string taut. Where do you see two centrifugal forces? And how can centrifugal force be a reaction to anything. I have a quote from you here,

in the inertial frame, it's the reaction to the force with which the string is accelerating the balls. Dicklyon (talk) 23:14, 26 April 2009 (UTC)

That quote is totally nonsensical. It is a desparate attempt to try and argue the impossible. The centrifugal force is not a reaction to any other force. It exists in its own right by virtue of absolute rotation. David Tombe (talk) 23:50, 26 April 2009 (UTC)

The equation for the forces and accelerations along r is a 1D frame rotating at rate theta-dot. I'll take this opportunity to swoop out now; but feel free to explain what you mean by "absolute rotation" in the case of the ball moving in a straight line with a limp string attached. Dicklyon (talk) 01:43, 27 April 2009 (UTC)

Dick, You have completely avoided the question. There is an outward centrifugal force acting on the ball even before the string gets pulled taut. That is the centrifugal force as per equation 3-11 in Goldstein. It then pulls the string taut. Where do you see two centrifugal forces in all of this? And how can you see the centrifugal force as being a reaction to the centripetal force when the centripetal force doesn't even come into existence until the string has been pulled taut? And why do you feel the need to insert a frame of reference around the problem? Can you not clearly see what is going on without involving a frame of reference? David Tombe (talk) 10:05, 27 April 2009 (UTC)

We could explain it to you if you understood vector notation. Do you understand vector notation?- (User) Wolfkeeper (Talk) 17:18, 27 April 2009 (UTC)

David, your example makes it very clear what the two different centrifugal forces are. The motion is purely is linear, yet there is a centrifugal force, from the point of view of an observer watching the ball approach and recede and looking at the second derivative of the distance r as a generalized acceleration. On the other hand, the string is slack, so since it's not pulling on the ball it feels no reaction force. The reactive centrifugal force is zero (until the string goes tight), and "fictitious" centrifugal force is nonzero, in theis case of straight line motion. The "fictitious" one doesn't correspond to any real curved motion or rotation, just the rotating point of view from which the observer measures the ball's location in one dimension r. Dicklyon (talk) 17:55, 27 April 2009 (UTC)

Dick, I didn't see your two centrifugal forces in that explanation. What is wrong with the simple explanation that the centrifugal force which acts on the ball then causes the ball to pull the string taut? David Tombe (talk) 20:35, 27 April 2009 (UTC)

What's wrong is that it's just words, with no interpretation that I can figure out. Dicklyon (talk) 23:29, 29 April 2009 (UTC)

Why do we need a frame of reference?

Tombe: Dick, You have completely avoided the question. There is an outward centrifugal force acting on the ball even before the string gets pulled taut. That is the centrifugal force as per equation 3-11 in Goldstein. It then pulls the string taut. Where do you see two centrifugal forces in all of this? And how can you see the centrifugal force as being a reaction to the centripetal force when the centripetal force doesn't even come into existence until the string has been pulled taut? And why do you feel the need to insert a frame of reference around the problem? Can you not clearly see what is going on without involving a frame of reference? David Tombe (talk) 10:05, 27 April 2009 (UTC)

The nail has been hit on the head. Can't what is going on be seen without a frame of reference? That is what the article has to answer clearly.

One key objective of mechanics is to relate "what is going on" so every observer can agree. Every observer can agree that the water in the bucket is concave. That is "what is going on".

Not everybody has the same explanation, however. They all try to apply Newton's laws to explain the curved surface. Some can do it using only gravity and the observed rate of rotation. Others can do it too, but gravity and the observed rate of rotation are insufficient. The worst disagreement is for the co rotating observer. Their rate of rotation is zero, but their gravity is identical to everybody elses. To explain why the water is not flat, they say there is a centrifugal force. Some observer's don't need that. Some observer's see a bit of rotation, and need a bit of centrifugal force, but not as much.

There's the rub. "What is going on" is the same for everybody. How they analyze and explain differs.

The explanation is not a "gut feeling" issue. It is an issue of calculation. The input data is the curvature of the water, and the observed rate of rotation, and the gravitational force. Using these data, explain the observed curvature using the math of Newton's laws. Set up a force equation. Calculate the result.

Not every observer has the same rate of rotation. Their dot-theta on the "a" side is observed dot-theta, which differs for different observers. What they put into the Force side of F=ma also differs. Some don't need centrifugal force. Some do. It depends upon the dot-theta term on the "a" side. That is input data that changes with the observer. The force side compensates. Everybody gets the same differential equation for F=ma, does the same math, and finds the same curvature, of course.

Scientists are prejudiced. They like fewer terms on the force side of the equation, and if they can do that by choosing some particular frame of reference, they go for it. So centrifugal force is regarded as necessary for some observers, but they are the unfortunate ones. The "reality" is that no centrifugal force is needed on a "fundamental basis". The observers for whom the "right" dot-theta is observed, the ones that need no centrifugal term on the "F" side, are the "chosen ones", the observers that see "reality".

This slippery slope applied to the disappearance of magnetic forces for some observers leads to special relativity. The disappearance of gravity for some observers leads to general relativity. Brews ohare (talk) 13:52, 27 April 2009 (UTC)

Brews, central force problems are two dimensional and we are all agreed that this is the radial equation,

${\displaystyle m{\ddot {r}}-mr{\dot {\theta }}^{2}=f(r)}$

It is equation 3-11 in Goldstein. You are now telling us that only certain observers need the centrifugal force term. What is fundamentally different between the centrifugal force and the centripetal force such that the centripetal force can be observed by all observers, whereas the centrifugal force can only be observed by co-rotating observers? They are both rotating. They both act in the radial direction. One is inverse square law. One is inverse cube law. The different power laws account for orbital stability. David Tombe (talk) 16:11, 27 April 2009 (UTC)

The equation from Goldstein presumes a frame of reference. That begs the question. Brews ohare (talk) 18:51, 27 April 2009 (UTC)

Brews, the assumed frame of reference is the inertial frame of reference. All the variations of the radial and transverse unit vectors are relative to the inertial frame of reference. Rotating frames of reference don't enter into it. Why are you happy with the concept of a rotating centripetal force being viewable from the inertial frame whereas you can't cope with the idea that we might equally view a rotating centrifugal force from the inertial frame? What is this special problem with centrifugal force that makes people think that we need to be in a rotating frame in order to be able to view it? I can watch somebody swinging a bucket of water over their head and see the centrifugal force in operation. I don't need to be swinging with the bucket to see the centrifugal force. David Tombe (talk) 20:42, 27 April 2009 (UTC)

David, if you want to be in the inertial frame, you can't call the second derivative of r an acceleration; it's a generalized acceleration in the rotating frame or the fictitious 1D frame, but in the inertial frame it's not, as the freely-moving ball makes clear; when there's no acceleration of the ball (it's moving in a straight line), you still have a non zero r-double-dot. You can't have it both ways – either use the acceleration in the inertial frame, or use the frame in which the acceleration is r-double-dot (or has r-double-dot as a component in the 2D case). Dicklyon (talk) 20:47, 27 April 2009 (UTC)

David: I went to some length above about the bucket, and made what seems to me to be a lucid explanation of matters. You can find the mathematical details at bucket argument. You can similarly see the mathematical details of the ball & string argument at rotating spheres. The whole point is that dot-θ is an observed value, and is different in different frames. Thus, even if we all use the same radial equation, and the same origin, and see the same ball running about, our ma side of the equation differs from one to another. As there is only one equation that works, two observers with different dot-θ terms on the ma side have make their equations agree by adding different forces on the force side. That is where the centrifugal force comes in – to patch things up. Brews ohare (talk) 21:13, 27 April 2009 (UTC)

Dick, how come the second time derivative of r can be called an acceleration in relation to the centripetal force, even when the centripetal force is rotating? Who told you that it can't be called acceleration in relation to the centrifugal acceleration? You can call it Harry if you like but it won't make any difference to the physics. But you are actually trying to tell me that I am not allowed to call the centrifugal acceleration an acceleration. You are playing on words to avoid answering the key question. What is wrong with saying that the centrifugal force on the ball then causes the string to be pulled taut? Where are the two centrifugal forces that you are talking about? Your explanation above did not make any sense. David Tombe (talk) 22:21, 27 April 2009 (UTC)

What are you talking about? Under what circumstance did anyone say that it's an acceleration with respect to one force and not another? Are you making up stuff to object to? I'm sorry my explanations don't make sense to you; it seems to be a problem unique to you; similarly with the explanations of others that are understood except by you. Dicklyon (talk) 23:22, 27 April 2009 (UTC)

Dick, it says in the book that it's a central force equation. If the centripetal force is a force, how could the centrifugal force term in the same equation not also be a force? You have just said above that the centrifugal term is not an acceleration. And don't try to pretend that you are part of some united front. Wolfkeeper says that he believes it's a real force, whereas you have said that it is only a fiction. So don't try to pretend that your speaking as a spokesman for a group that are all saying the same thing. David Tombe (talk) 01:56, 28 April 2009 (UTC)

David, I never said it's "not a force", nor that it's "only a fiction." I said it's a "fictitious force", which is the other common term for what Wolfkeeper calls a "pseudoforce". I don't really care what you want to call it, just recognize that in a non-rotating frame it goes to zero, unlike the centrifugal reaction force. Dicklyon (talk) 03:48, 28 April 2009 (UTC)

Brews, Yes, there is a different centrifugal force acting on one object relative to every point in space. That is part of the mystery of it. But we can deal with that later. At the moment we have a simple radial equation with a centrifugal term which can pull a string taut. There seems to be a great reluctance to boldly print this equation in the article without hiding it behind hedges, and then to openly and unashamedly name the terms in it. David Tombe (talk) 22:21, 27 April 2009 (UTC)

Dick, here is your exact quote,

But we'd need to get you to accept that "the outward centrifugal force" of a ball moving in a straight line with a slack string attached is a fiction Dick Lyon 19.22 hours 26th April 2009

Wolfkeeper says that it is real. So your united front does not exist.

And furthermore, you did try to argue that the centrifugal term is not an acceleration. You clearly stated above that the second time derivative of the radial distance r is not an acceleration. And I'm not going to waste time on word games as between force and acceleration. The two terms are interlinked through F = ma and so they are to all intents and purposes interchangeable in this discussion. Quibbling over force versus acceleration is another of the standard decoy methods used when people are trying to deny the existence of centrifugal force in the face of overwhelming evidence to the contrary. They swing into acceleration, or they swing into Cartesian coordinates. Anything rather than facing up to the reality that the centrifugal force pulls the string taut. David Tombe (talk) 11:36, 28 April 2009 (UTC)

Oops, sorry, I misspoke; I meant "is a fictional force" (in the usual sense that it's zero if viewed from an inertial frame, which is why the ball is moving in a straight line). Dicklyon (talk) 15:24, 28 April 2009 (UTC)

Yup, although just because it goes to zero in a stationary reference frame doesn't make it not real. Kinetic energy goes to zero in at least one inertial reference frame too. Everyone here gets this David, they may phrase it differently, but they all basically have the same understanding. David you're not editing from a good-faith position- you're trying to introduce your own OR into the article. You're trying to edit the article to be compatible with you wacky theories about how centrifugal force is the cause of magnetism or whatever. But, strangely enough, there's no good references that support that POV; so we cannot really let you insert it here, in the wikipedia, and nor can we allow you to modify/distort the article to make it more compatible.- (User) Wolfkeeper (Talk) 16:04, 28 April 2009 (UTC)

If you have novel physical theories you need to take them to a respected journal and publish them there, rather than trying to get them as accepted physics by editing the wikipedia.- (User) Wolfkeeper (Talk) 16:04, 28 April 2009 (UTC)

Wolfkeeper, you have just said that it can be zero and still be real. How can a real force of zero value pull a string taut? You have indicated that you don't comprehend this topic. The planetary orbital equation is not my own original research. It is a topic which is being sidelined because it contradicts the superficial approach to centrifugal force which dominates the modern textbooks. You have all been trying to distort the topic of planetary orbits in order to bring it into line with your own misinformed opinions which are based on the topic 'rotating frames of reference'. David Tombe (talk) 16:15, 28 April 2009 (UTC)

If I drive my car down the road, there is a frame of reference in which the kinetic energy of my car is zero. How can zero kinetic energy move me? That's the same logic as yours.- (User) Wolfkeeper (Talk) 18:39, 28 April 2009 (UTC)

Really, if we add up the megabytes of drivel you've 'contributed' to the wikipedia, how much have you cost the project, a charity in total?- (User) Wolfkeeper (Talk) 18:39, 28 April 2009 (UTC)

Wolfkeeper, you'd need to lay out the analogy point for point. David Tombe (talk) 20:37, 28 April 2009 (UTC)

Dick, it's not zero in any frame of reference. It pulls a string taut. Equation 3-11 in Goldstein,

${\displaystyle m{\ddot {r}}-mr{\dot {\theta }}^{2}=f(r)}$

is all that is needed to comprehend the situation. The centrifugal force is an outward radial force which acts between any two objects which have mutual tranverse speed. You are introducing unnecessary complications such as rotating frames of reference, fictitious forces and one dimensional equivalent equations in order to try and mask out this simple underlying reality. David Tombe (talk) 16:07, 28 April 2009 (UTC)

What does that evaluate to when theta dot is zero? What is theta-dot? Does it depend on the frame of reference, or not? What is this force acting on when there's no string? Why isn't it causing any acceleration? Dicklyon (talk) 17:00, 28 April 2009 (UTC)

Dick, when the theta dot is zero there won't be any centrifugal force at all. Theta dot is the angular velocity of the balls relative to the inertial frame. When theta dot is non-zero there will be a centrifugal force acting on the balls, string or no string. Such a centrifugal force acts on the Moon without the involvement of any string. That centrifugal force causes a centrifugal acceleration ${\displaystyle r{\dot {\theta }}^{2}}$.

Equation 3-11 covers every case scenario. If the centripetal term is a negligible gravity term, then the orbit is hyperbolic. If we then attach a string, the centrifugal force will pull the string taut. The tension in the string will then induce a centripetal force (on top of the already existing gravity) and a circular motion will ensue. David Tombe (talk) 18:27, 28 April 2009 (UTC)

Parts of that are OK; but what does it mean when you say "When theta dot is non-zero there will be a centrifugal force acting on the balls, string or no string"? Where is the acceleration corresponding to this force? If there's a centrifugal force acting on the balls, why do they keep moving in a straight line (with no string)? There's no acceleration (no x double dot or y double dot in the inertial frame), just an r double dot (a coordinate in a rotating 1D frame). Dicklyon (talk) 01:50, 29 April 2009 (UTC)

Dick, OK, let's drop the string and let's have a pure planetary orbit. Let's have negligible gravity and hence a hyperbolic orbit. There will be an outward radial acceleration on each of the planets, and that outward radial acceleration will have the value ${\displaystyle r{\dot {\theta }}^{2}}$. It is a two dimensional problem and not a one dimensional problem as you have claimed. If it were a one dimensional problem, then there would be no transverse motion and neither could there be any ${\displaystyle {\dot {\theta }}}$. David Tombe (talk) 09:25, 29 April 2009 (UTC)

In the case we're talking about, with negligible gravity, the "orbit" is a straight line, right? Which means that in the inertial frame, the "planet" has no acceleration, right? Dicklyon (talk) 19:53, 29 April 2009 (UTC)

Dick, in the inertial frame, the planet moves in a straight line just as you say. It has an outward radial acceleration of magnitude ${\displaystyle {\dot {\theta }}}$.

Exactly so; but an "outward radial acceleration" is not an acceleration. The accleration is zero in that inertial frame, corresponding to the lack of force on the ball; the x double dot and y double dot (and z double dot if you want that dimension, too) are all zero, corresponding to straight-line motion, right? By looking at "radial accleration" it's equivalent to saying rotate your measurement direction at rate theta dot to point at the ball, and meaure the generalized location, velocity, and acceleration in that rotating frame; in that frame, there's an apparent centrifugal force, unlike the zero force in the inertial frame where the acceleration is zero. If you're claiming that the ball moving in a straight line in an inertial frame has a nonzero acceleration in that frame, then I'll have to pull my hair out in despair. Dicklyon (talk) 23:28, 29 April 2009 (UTC)

Dick, gravity causes an inward radial acceleration, which may or may not be rotating. So why can an outward radial acceleration, as caused by centrifugal force, not also qualify as an acceleration in your books? Cartesian coordinates don't come into this. Gravity and centrifugal force are both central forces, and we use polar coordinates to deal with central forces. The two variables r and θ are both measured relative to the inertial frame and so we are dealing with the inertial frame of reference using polar coordinates. Rotating frames of reference don't enter into the problem. Gravity and centrifugal force are both radial forces and they both cause radial accelerations. And both of these radial forces are real. The centrifugal force can pull a string taut and it can undermine gravity so as to hold the planets in their orbits. And there is only one centrifugal force. The article has been split due to a lack of comprehension of the topic. David Tombe (talk) 11:03, 30 April 2009 (UTC)

No, actually, gravity is, from Einstein's equivalence principle, an acceleration of the reference frame. And gravity isn't always a central force either; that's only approximately true in spherically symmetric situations; in the general case you have one oddly shaped object attracting others, and the centre of gravity isn't even at the centre of mass.- (User) Wolfkeeper (Talk) 13:40, 30 April 2009 (UTC)

Wolfkeeper's diversion outside of classical mechanics being quite irrelevant to the point, gravity causes an acceleration that appears in the cartesian coordinates of the path of an object viewed in an inertial frame, while centrifugal force does not. If you want to use polar coordinates, you need to recognize that second derivatives of those are not accelerations, but need to be related to accelerations via the transformations that Brews has described. If you use second derivative of r as acceleration, that only makes sense in a frame that's rotating such that r is a cartesian coordinate in that frame. I've never seen any indication in any book, Goldstein or otherwise, that any classical physics can be made to work doing it otherwise. What could F=ma mean if we didn't have at least this much understanding of acceleration? Dicklyon (talk) 14:56, 30 April 2009 (UTC)

No, no. My point is that even in newtonian terms gravity is a central force in the two-body conservative force sense, but in non symmetric cases it's not necessarily radial; the centre of mass and centre of gravity do not in general align even in newtonian calculations.- (User) Wolfkeeper (Talk) 15:02, 30 April 2009 (UTC)

Right, I see; it's a confusion invoked by David's mystical concept of "central" that you're trying to clear up; thanks. Gravity acts toward another body; centrifugal force acts toward whatever point you choose to measure r from. One is not dependent on the frame (but is "central" in the center of mass frame), the other is totally frame dependent, always acting toward whatever point you choose to look from. Dicklyon (talk) 15:27, 30 April 2009 (UTC)

Dick, I'm going to ignore Wolfkeeper's diversions regarding relativity and assymetrical shapes. The concept of a central force is not a mystical concept of my creation. You have however raised a very interesting point which I have always been fully aware of. You have pointed out how centrifugal force can be relative to any arbitrarily chosen point in space whereas gravity can only be relative to a physical centre of mass. You have also correctly pointed out how centrifugal force disappears in Cartesian coordinates. That is not however the same thing as disappearing in the inertial frame.

These somewhat mysterious facts can help us to understand the underlying physical nature of centrifugal force. But at the moment I am merely trying to lay equation 3-11 from Goldstein on the table, and name the terms in it. This could be done in a very short section which would replace Brews's long section on planetary orbits. Brews's section is technically correct but it is too long winded for the purposes of this article and it also plays down the star piece, and doesn't even mention it by name.

My guess is that because centrifugal force possesses the strange properties mentioned above, such that it somewhat blends into Euclidean geometry, that this is what causes all the trouble. An equation such as 3-11 can expose it as a real outward physical force, yet on the other hand it doesn't show up in day to day situations that are described in terms of Cartesian coordinates. But that is not a reason to shy away from the reality that the ${\displaystyle mr{\dot {\theta }}^{2}}$ term in equation 3-11 is the familiar centrifugal force that holds the planets up in their orbits. David Tombe (talk) 16:38, 30 April 2009 (UTC)

David, you speak nonsense; you want the force to be "real", not frame dependent, but dependent on where you measure it from and on what kind of coordinate system you measure it with. This is not physics. No wonder it's "mysterious" in your way of looking at it. Dicklyon (talk) 18:35, 30 April 2009 (UTC)

Dick, Centrifugal force is real and it is not frame dependent. You are confusing inertial frames of reference with Cartesian coordinates. Cartesian coordinates mask the existence of the centrifugal force but they don't get rid of the reality of it. The reality of centrifugal force is expressed clearly in polar coordinates which are relative to the inertial frame. There is no need to introduce Cartesian coordinates into this debate. Cartesian coordinates hold no superiority over polar coordinates when it comes to ascertaining the reality of radial effects on either the astronomical scale or the microscopic scale.

And any rate, we don't need to discuss that. All we need to do is state equation 3-11 in Goldstein, name the terms in it, and point out that the centrifugal force term can pull a string taut and hold a planet up in its orbit. David Tombe (talk) 00:35, 1 May 2009 (UTC)

Requested move

Centrifugal force (rotating reference frame) should be moved to Centrifugal force because Centrifugal force already redirects here; it is the primary topic of "centrifugal force", and "centrifugal force" is the common name for this topic. Furthermore, the only reason I can find for the current title is that it was moved here by User:Ggsgas during a prolific move vandalism campaign last year. According to naming conventions, an article should not be disambiguated any further than necessary, and the parenthetical disambiguation here is truly puzzling. Wilhelm_meis (talk) 12:19, 30 April 2009 (UTC)

Wilhelm meis, I fully support your request to unite centrifugal force into a single article. The reason why it was split in the first place was because of what I would consider to be a specious argument. The argument ran that the centrifugal force as per this article acts on a different body than the so-called 'reactive centrifugal force' that is dealt with in the other article.

But anybody with a full comprehension of the topic can see that these two effects are merely two different aspects of the one force. Centrifugal force acts on body A. Body A then pulls a string taut. It is all one single force. But those who supported splitting the article would argue that the centrifugal force that acts on body A is one force and that the pulling of the string taut by body A, due to the centrifugal force acting on body A is another force. Feel free to unite the two articles if you wish. But I guarantee that you will encounter enormous opposition based on that specious argument which I have just shown to you. David Tombe (talk) 16:44, 30 April 2009 (UTC)

I also support a merge; there's no reason we shouldn't discuss both the reactive and fictitious force viewpoints in one article, even though David Tombe has a very idiosyncratic view of them that we'll have to continue to defend against. Until we merge, however, let's keep the topic specificity in the title and the hatnote. Dicklyon (talk) 18:37, 30 April 2009 (UTC)

This version of 27 April 2008 looks like the last sensible version, which the different viewpoints are made explicit up front; after that, Wolfkeeper submerged the reactive viewpoint and moved the article to be about only the fictional viewpoint; David fought everybody else for over a year, and Brews came in and over-expanded and complicated things. Can we move back to something sensible? Dicklyon (talk) 18:53, 30 April 2009 (UTC)

No Dick, that version was a total dog's dinner of confusion. David Tombe (talk) 00:41, 1 May 2009 (UTC)

Apart from the fact that this is a move review not a merge review, in the wikipedia articles are properly on one or or more synonymous meanings of the title. (That's the primary difference between an encyclopedia and a dictionary, the latter which usually contains multiple definitions per article, see Misplaced Pages:NOTADICT). Centrifugal force (in the rotating reference frame sense) and Centrifugal force (in the reactive force to the centripetal force) are anything but synonymous; they occur at different times to different bodies, act in general at different directions and vary differently, and are defined differently and have different cardinality and are used for completely different purposes by different people. In short. Hell No.. - (User) Wolfkeeper (Talk) 00:08, 1 May 2009 (UTC)

Wolfkeeper, you've got it all totally wrong. David Tombe (talk) 00:39, 1 May 2009 (UTC)

There is no right or wrong here, there's only well referenced material. Unfortunately, you don't have any.- (User) Wolfkeeper (Talk) 13:24, 1 May 2009 (UTC)

Actually, I requested a move, not a merger. If there is consensus to merge as well, I have absolutely no problem with that, but the simple title should not be a redirect to a senselessly disambiguated title. If someone wants to propose a merger, please do, but this is supposed to be a move discussion. Can I get everyone's thoughts on moving this article to Centrifugal force? I think it's important to have two separate discussions, one for moving and one for merging. Thanks. Wilhelm_meis (talk) 23:44, 30 April 2009 (UTC)

• Oppose. The title helps the user understand what we are talking about and helps disambiguate it when there is more than one topic that goes with that name.- (User) Wolfkeeper (Talk) 00:08, 1 May 2009 (UTC)

So are you arguing that this is not the primary topic of "Centrifugal force", or that there is no primary topic? It seems that there may well be consensus (with a holdout or two) that these are closely enough related topics to merit a merger, as one unified topic, but, again, I don't want to digress into a merger discussion. I'm just trying to clarify the consensus of what is the primary topic. Again, it makes no sense to have Centrifugal force redirect to a needlessly disambiguated title. Either this is the primary topic or it is not. Wilhelm_meis (talk) 04:47, 1 May 2009 (UTC)

• Support. I support move and/or merger. Anything to get the topic unto one page. David Tombe (talk) 00:36, 1 May 2009 (UTC)

• Comment. It is completely ridiculous to have three separate articles about the same subject, and it really constitutes a three-way wp:content fork. One article says there isn't really a force, one says it is a fictitious force, and the third says it is really a centripetal force. Make up your mind and pick one name for the article, please, not three articles. Hint: Don't call it centrifugal force - there is no such thing, and please lose the hatnote "For the general subject of centrifugal force, see Centrifugal force (disambiguation)", and especially don't try to make a disambiguation page into an article about the confusion about which of the three content forks to go to. 199.125.109.102 (talk) 04:43, 1 May 2009 (UTC)

Agreed. Mostly. I would argue that we should place the article at Centrifugal force because this is the common name used in English. If we want to talk about the misconceptions inherent to the common term, fine, by all means, let's please do that, but let's also put it where it is easy to find and usable to the general reader. I agree that the present situation defies common sense, but we need to set aside some of our disagreements over the finer points of definition and produce something useful to the general reader. Then we can worry about making it more technically accurate. Of course, it also helps if we avoid original research and synthesis and stick with what is published in reliable sources. Don't get me wrong - I'm not accusing anyone of anything, but I think several editors here have become somewhat impassioned on the subject, and perhaps could better help the project by taking a deep breath and thinking objectively about the overall quality of the article(s). Wilhelm_meis (talk) 04:56, 1 May 2009 (UTC)

No, no, no, and no again, you can not call it centrifugal force even if every person on the planet who has not taken physics (and that is over 99%) calls it centrifugal force. There is no such thing, it is centripetal force. You need to redirect centrifugal force to centripetal force and point out what it really is in the article, and cover it in one article, not three. Content forks are prohibited, and that is all that these three articles are - it would be like having two articles about the earth, one insisting that it was flat, and the other insisting that it was not. 199.125.109.88 (talk) 03:13, 2 May 2009 (UTC)

Actually, as wikipedia editors, we don't get to decide what to call it; we're supposed to report on what things are and what they're called, not try to enforce our own logic of what things should be called. But you're confusing the centrifugal (outward-directed) and the centripetal (inward-directed) forces; that's one more POV that we haven't heard from recently. Dicklyon (talk) 03:23, 2 May 2009 (UTC)

Dicklyon is absolutely right on this point. It is not our place as Wikipedians to prescribe what term people ought to use, but rather to describe what term people commonly use. Please refer to WP:UCN and WP:NOT (especially note that WP is NOT a publisher of original thought, a soapbox for advocating a particular position - and yes this applies to physics as well as politics - nor is WP a textbook. Misplaced Pages is an encyclopedia, and like any other encyclopedia, intended for the GENERAL READER. That is where these articles are most deficient. As to the argument against moving, no one has yet explained why this article should retain its parenthetical disambiguation AND be the target of a redirect from the simplified title. If anyone can explain that to me, then I will be satisfied enough, but otherwise, I fully intend to see this article moved to Centrifugal force. Then the pedantic professors can resume squabbling and bickering over its content while its readability continues to suffer tremendously. Wilhelm_meis (talk) 12:37, 2 May 2009 (UTC)

• Support. It's a step toward reunification, so let's do it. I disagree with Wolfkeeper's rationale "The title helps the user understand what we are talking about and helps disambiguate it when there is more than one topic that goes with that name" because I think that we should not keep the article so narrow that it can't compare and contrast the different viewpoints on centrifugal force; what we have now is a POV fork, which is generally frowned on. Dicklyon (talk) 05:34, 1 May 2009 (UTC) see new opinion below

There is no unification. They're completely different forces. One is a real force you get in all references frames, the other you only get in rotating ones and is a pseudoforce. One was discussed by Newton (reactive) but the rotating reference frame was completely unknown to him. One is a D'Alembert force, the other, not. The only thing they have in common is the name. They are NOT synonymous. They are NOT defined in the same way, or even similar ways. The wikipedia does not have multiple definitions of a single term unless there is significant overlap other than the name. In this case... just the same name. Oh and they point away from a centre. But different centres. Oh and reactive centrifugal force isn't associated with a coriolis force... but this one is. This is the sister article to coriolis effect, it is completely distinct from the reactive centrifugal force in every important way.- (User) Wolfkeeper (Talk) 13:12, 1 May 2009 (UTC)

• Oppose. Given the apparent intransigence of the various people who like the different points of view, or like them separate, a better idea is to write a short article at Centrifugal force in summary style, to link the rotating frame and reaction articles that can then keep their bloated form. Dicklyon (talk) 23:51, 1 May 2009 (UTC)

Merge proposal

As long as we're working on the move question, let's also consider the merge question that opened above. I've added a mergeto on Reactive centrifugal force and a mergefrom here. I notice that Reactive centrifugal force already has a section on the fictitious force in a rotating frame; and this article has a lot of bloat; so that merge would need to get rid of a lot of stuff. I think it would be a big win, if people don't hang tightly to the current big mess. Dicklyon (talk) 05:41, 1 May 2009 (UTC)

• Support as nominator. Dicklyon (talk) 05:41, 1 May 2009 (UTC)

• Support. I agree. The more I dig into this topic, the more I see that these articles really are looking at the exact same phenomenon from different perspectives (which would make them WP:POVFORKS). The whole thing about "rotating reference frames" is just to give the observer a more subjective viewpoint to make the same "force's" effects easier to understand in certain applications. The problem I find with it is that we have what amounts to a POV fork buried under a slew of jargon to befuddle the general reader with endless mathematical formulae, instead of explaining the concepts in a clear and concise way like this and this. What I see is that while editors have focused on the minutiae of verbiage, the overall articles have suffered until they are barely understandable to a casual reader. Please remember, not everyone who reads WP has a Physics degree (or even an 8th grade understanding of Math!). I think we need to get it much more geared to the general reader. That's my $2x10. Wilhelm_meis (talk) 06:22, 1 May 2009 (UTC)

Wilhelm, If you carefully read through the past debates, you will see that that is exactly what I have been trying to do. I have consistently argued for one single article with a short introduction describing the centrifugal force as the outward force that is associated with rotation. More recently I have been trying to get a consensus to drastically reduce the planetary orbital section to a small paragraph which simply states the central force equation 3-11 out of Goldstein's 'Classical Mechanics', names the terms in that equation, and points out the fact that the centrifugal force term can pull a string taut. As for the so-called reactive centrifugal force, there is no such thing. Those that are advocating such a concept as a separate existence are referring to the effect of pulling a string taut by virtue of it being attached to an object which is experiencing centrifugal force. David Tombe (talk) 10:38, 1 May 2009 (UTC)

I too would encourage people to read the archives. They mostly show that David Tombe has been spamming the talk page over a considerable period with his views, and completely misunderstands the physics. Among other things he thinks that coriolis effect only acts at right angles to the central rotation axis, whereas anyone who knows cross products (i.e. not Mr. Tombe) can immediately see that the equation says that coriolis acts at right angles to the velocity- which is by no means constrained to be radial. In short, he's in my (at least somewhat educated) opinion, a crank. A crank that has been banned for spamming his drivel here before; and with any luck will be again. He also thinks that relativity theory is wrong, and that magnetism is a form of centrifugal force. Needless to say this is not the neutral point of view. Essentially every edit he makes tries to distort the article towards this point of view. If you actually make any edit and Tombe agrees with it, there's a very high chance that you've messed up. In this case, coriolis force and centrifugal force come out of the same equation; one that does not give you reactive centrifugal force. If anything there is a much stronger case for merging coriolis and centrifugal force together- they are a pair.- (User) Wolfkeeper (Talk) 14:42, 1 May 2009 (UTC)

Wolfkeeper, anybody who has seen the transverse planetary orbital equation should know that the Coriolis force is exclusively a transverse force. David Tombe (talk) 22:39, 1 May 2009 (UTC)

Sure, that's true. For polar coordinate analysis there is an angular acceleration due to changes in the radial distance. But in rectangular coordinates (that this article is about) there's an inward and outward force when the body moves circumferentially and in general there is a force that acts at 90 degrees to the motion. If you understood this you would never make the incorrect general statements you are continuing to make. It is my opinion based on your statements over that you are incapable of understanding this article. I find this sad, but I'm not about to let you dumb the article down.- (User) Wolfkeeper (Talk) 00:34, 2 May 2009 (UTC)

Wolfkeeper, that's an argument for the Coriolis force page. It seems to me that you are incapable of understanding the implications that are inherent in the derivation that leads to the rotating frame transformation equations. If you understood that properly you would see that it is identical to the polar coordinate derivation, and that it is all one single topic and that Coriolis force is a transverse force that is linked to conservation of angular momentum and Kepler's second law. As for rectangular coordinates, the coordinate system doesn't effect any realities. But who would ever think of using rectangular coordinates for situations such as centrifugal force which are totally suited to polar coordinates? This business of continuing to introduce Cartesian coordinates is just a diversion to cloud the issue. David Tombe (talk) 10:07, 2 May 2009 (UTC)

I wouldn't agree that the article is tied to rectangular coordinates; the physics doesn't depend on this. But it has to be recognized that the r dimension is a dimension in a rotating reference frame, a fictitious 1D rotating system. This is what David is unable to relate to. And no matter how you do it, Coriolis force is a fictitious force, just like centrifugal force, that depends on velocity in the rotating system, as opposed to the centrifugal that just depends on position. In the 1D fictitious system, it plays no role, since there's no motion except along the radial. Dicklyon (talk) 01:24, 2 May 2009 (UTC)

• Oppose They are completely different. One is a real force, the other is a pseudoforce. They act around different centres, were invented at different times, and share only a name. The wikipedia is not a dictionary. The real force can have multiple centres in any frame, while the pseudoforce, only one. etc. etc.- (User) Wolfkeeper (Talk) 13:26, 1 May 2009 (UTC)
• Support. I also see the two articles as describing different aspects of the same phenomenon. -AndrewDressel (talk) 13:30, 1 May 2009 (UTC)
• Oppose. Wolfkeeper is entirely right: one is a force the other a pseudoforce; moreover, the examples given in the two articles illustrate different phenomena and different methodology. It is not going to make things clearer if some of these examples are deleted, or the contrast between them has to be continually made throughout a combined article. Finally, if there are supporters of a merger on the basis that the two topics really are one, it behooves them to explain away the differences in this table:

Brews ohare (talk) 22:27, 1 May 2009 (UTC)

Explaining the differences in that table is exactly what the article would need to do; we don't need to do it here, as nobody is claiming that these two things are "the same"; just that they are the different facets of the topic of centrifugal force. Dicklyon (talk) 22:54, 1 May 2009 (UTC)

As a matter of clarity, it's better to keep separate topics separate. I believe this talk page and the one on reactive centrifugal force both illustrate clearly that separation is the wiser course. For example, it took inclusion of the exploded force diagrams on the reactive force page to convince many just how the reactive force was to be understood. Brews ohare (talk) 00:23, 2 May 2009 (UTC)

• Support. There is no such thing as the reactive centrifugal force. The effect which is being discussed in that article is a knock-on effect on another object, ultimately caused by the one and only centrifugal force. And that knock-on effect is most certainly not reacting to any centripetal force. It exists in its own right. The references in that article which use the term 'reactive centrifugal force' are not even referring to the effect which is being covered by that article. For example, the so-called reactive centrifugal force acting on the Sun is the one and only centrifugal force as per equation 3-11 in Goldstein. David Tombe (talk) 22:39, 1 May 2009 (UTC)

Other merge proposal

It has also now been proposed that this article be merged to centripetal force. Dicklyon (talk) 03:51, 2 May 2009 (UTC)

• Support. The subject needs to be covered, and explained, in one article only, at Centripetal force. Splitting it into three POV's is prohibited. One of the first things you learn in physics is that when you swing a bucket over your head that isn't a centrifugal force you are feeling, it is a centripetal force (but how would you know, every force produces an equal and opposite reaction - Newton's Third Law of Motion). 199.125.109.88 (talk) 03:35, 2 May 2009 (UTC)

• Oppose. You cannot merge centripetal force and centrifugal force. They are two different forces. In the planetary orbital equation, the centripetal force is gravity and it is an inward force, whereas the centrifugal force is an outward force. In general, the centripetal force is an inward force supplied by something like gravity, or the tension in a string, or the normal reaction from the floor of a rotating cylinder. Centrifugal force is an outward force that is induced by absolute rotation. There can be no question of merging centripetal force with centrifugal force. That truly would mess it all up. The only topic that all these concepts can be dealt with together in a unified fashion is Kepler's laws of planetary motion. But if you go to that page, you will see that the same obstructions are present. There is a prohibition on using the names centrifugal force and Coriolis force for two of the terms in the equations. David Tombe (talk) 09:28, 2 May 2009 (UTC)
  • See below. Referred to Jimbo. 199.125.109.88 (talk) 17:19, 6 May 2009 (UTC)

Note to Wilhelm

Wilhelm, you've suggested the clear explanations at this and this. But the latter calls the topic of this article "false", and asserts that "An evil word has worked its way into our daily vocabulary, and with it, an incorrect understanding of the way physics works. 'Centrifugal Force'." This is nonsense; there are only a few people who have that "incorrect understanding", and there's no reason to apply the term "false" to a "fictitious force" that often conveniently and correctly used in mathematical physics. It is, after all the entire topic of this article we're working on. Dicklyon (talk) 16:11, 1 May 2009 (UTC)

I never suggested that we should copy those pages, and I certainly did not mean to imply that in any way. I was only pointing out that these concepts can be explained in a more clear and concise way than what we currently have. Please do not take my suggestion as a full endorsement of those pages! Wilhelm_meis (talk) 01:58, 2 May 2009 (UTC)

A great source

I finally found a book that goes into the whole "fictitious" treatment in a smart way, including the history of different conceptions from Newton and Leibniz (who apparently first came up with Goldstein's formula for radial acceleration as a difference between the gravitational and centrifugal terms). here. Dicklyon (talk) 19:06, 1 May 2009 (UTC)

This source says:

"Newton and Leibniz are using the term centrifugal force in different senses."

Exactly. This article is not dealing with the Leibniz sense, and introduction of this different meaning is simply confusing, and brings nothing to the understanding of centrifugal force as opposed to a narrow designator of a term in polar coordinates that possesses no relation to a true force, including especially a complete failure to transform as a vector.Brews ohare (talk) 22:36, 1 May 2009 (UTC)

I don't think so. The Newton sense is the reactive force (which David says doesn't exist); the Leibniz and Goldstein sense is the pseudo-force in a 1D system along the line between two bodies (which you say is not a centrifigal force?), which is not really different from the fictitious force that this article is about, is it? Dicklyon (talk) 22:51, 1 May 2009 (UTC)

No Dick, the Newtonian sense as per that article is an oversimplistic sense which assumes circular motion and a centripetal force which is equal and opposite to the centrifugal force. The Leibniz sense involves an equation which is the same as the equation which would hold for the equivalent 1-D problem. You still need to accept that Goldstein did not actually say that equation 3-11 itself was a 1-D problem. Basically Leibniz was looking at the general situation whereas Newton was stuck in the special case of circular motion. David Tombe (talk) 22:56, 1 May 2009 (UTC)

Dick, That was a very interesting article. Thanks for that. It seems that all along I have been looking at the problem from the same perspective as Leibniz without realizing it. Goldstein has clearly taken a Leibniz perspective on the issue and this entire edit war was because I was trying to introduce that perspective into the article. I knew that it was in Goldstein, but this time last year when the edit war began, I didn't have access to a Goldstein and I hadn't looked at my old copy for about 27 years. And my attempts to introduce that perspective were being thwarted under false accusations of original research.

That is an excellent article. I'm glad that you have brought it to my attention. It also clears up alot of other things which I had heard over the years but never followed up. Apparently there was alot of bitterness between Newton and Leibniz. I've also read that Newton got a bit twisted about centrifugal force. On the one hand, he believed in it and advocated it in his bucket experiment, but when Hooke started using it, Newton started to change the emphasis in planetary orbits to centripetal force. I can see myself now beginning to side with Leibniz in that great historical dispute. David Tombe (talk) 22:49, 1 May 2009 (UTC)

Where Newton says "Centrifugal force is always equal and opposite to the force of gravity by the third law," he's clearly treating it as the reaction force; it doesn't matter if motion is circular or not. When he later uses that interpretation to criticize Leibniz by saying that his reasoning (and formula) imply r-double-dot equals zero, he's clearly misapplying one concept where the other is needed. Obviously that would lead to a circular orbit, but he knew that a circular orbit was the wrong answer, so that's not where he was coming from. He just didn't accept the pseudoforce that Leibniz was using implicity, as Goldstein does, by looking at derivatives of r, the coordinate in a fictitious 1D system. Dicklyon (talk) 03:34, 2 May 2009 (UTC)

Yes Dick, he's misapplying one concept where the other concept applies, and the concept which he is applying, ie. his 3rd law of motion, never applies across centrifugal force and centripetal force. Newton was being deliberately twisted because there was a long running bitterness betwen himself and Leibniz. David Tombe (talk) 09:32, 2 May 2009 (UTC)

A basis for a new unified article. Newton v.Leibniz

Recently I made this edit,

== Proposal for a shortened section on planetary orbits ==

This very short paragraph should take the place of the existing section.

Centrifugal force arises in planetary orbits. The radial planetary orbital equation,

${\displaystyle {\ddot {r}}=-G(M+m)/r^{2}+l^{2}/r^{3}}$

can be solved to show that planetary orbits are either ellipses, parabolae, or hyperbolae. See Kepler Problem. The inverse cube law term on the right hand side of the equation is the centrifugal acceleration.

We now know that this is the approach that Leibniz and Goldstein adopted. It contains every aspect of the topic in a single equation. If the gravity is negligible the orbit will be a hyperbola. If we then connect a string between the planets, the centrifugal force will pull the string taut.

The problem is that Newton didn't want to be in agreement with Leibniz even though the evidence is that Newton's earlier writings about comet orbits suggested that he was essentially in agreement with Leibniz. Newton therefore objected to the above formula on the grounds that the radial acceleration would always have to be zero. He based this objection on his own 3rd law that action and reaction are equal and opposite, and that centrifugal force and centripetal force are an action-reaction pair.

I can't agree with Newton on this point, but it is a viewpoint which appeared in older texbooks. It appears in the 1961 edition of Nelkon & Parker but was erased in the 1971 revision.

Nevertheless, this Newtonian viewpoint seems to be the basis for the concept of 'the reactive centrifugal force'.

A single unified article on centrifugal force should discuss both these perspectives. I personally go along with the Leibniz/Goldstein approach. David Tombe (talk) 00:28, 2 May 2009 (UTC)

Why do you have trouble accepting both views at once? Newton is defining an action/reaction pair between centripetal and centrifugal force; lots of people do that, and it's not hard to accept. The other concept of centrifugal force, which is not quite equal to this one when orbits aren't circular, is the "fictitious" or pseudoforce of this article, as used by Leibniz and Goldstein. I would agree with the idea of writing an article to discuss this, but fear that you'll continue to push to screw it up by not understanding the latter concept while not accepting the former. Dicklyon (talk) 03:38, 2 May 2009 (UTC)

The "centrifugal" force is the reaction to the centripetal force. Just like when you stand on the ground, gravity pulls you to the earth with the force of your mass times the gravitational constant. At the same time the earth is pushing back up on your shoes with an equal and opposite force, yet no one get confused and calls that "anti-gravity". It is only confusing because it sure feels like a centrifugal force when you swing a bucket over your head, but that isn't the force you are feeling - you are feeling the centripetal force of you pulling on the rope to distort the bucket from the path it would have taken had the rope not been there. The rope pulling back against you is not a force, it is the equal and opposite reaction to a force. 199.125.109.88 (talk) 04:16, 2 May 2009 (UTC)

No Dick, Newton was being twisted on this occasion. He couldn't bring himself to accept that Leibniz was correct and that indeed Leibniz had been effectively saying what Newton had been saying earlier. The centrifugal force and the centripetal force are not in general equal. And the centrifugal force is never a reaction to the centripetal force. Newton was quite wrong to apply his 3rd law of motion to this situation.David Tombe (talk) 09:20, 2 May 2009 (UTC)

Anonymous 199.125.109.88, by all means adopt the Newtonian approach to the matter. Many textbooks did up until the 1960's. But it is wrong. The centripetal force in those simple circular motion scenarios doesn't come into existence until the centrifugal force has already created a tension or a pressure. Centrifugal force cannot therefore be a reaction to centripetal force, and in the general planetary orbital situation the two are not even equal to each other. Also, 199.125.109.88 it does rather look like you are getting centrifugal force and normal reaction confused. David Tombe (talk) 09:20, 2 May 2009 (UTC)

So now I get to go over to the local college bookstore and look up Physics texts? Doesn't Wikibooks even have a physics textbook? Wasn't the 60s when new math came out and they started saying that 2+2=3, or 4, or 5, or something else, depending on which rotating reference frame you were in (or how high you were at the moment)? I really do not think there is anything I am confusing other than why are there three articles about the same topic? Let's see Wikibooks:Physics with Calculus/Mechanics/Rotational Motion has a section on centripetal acceleration, and Wikibooks:A-level Physics (Advancing Physics)/Circular Motion says "Centrifugal force does not exist. There is only one force acting in circular motion, which is known as centripetal force. It always acts towards the centre of the circle." Just a guess but I suspect that was written some time long after "the 1960's". 199.125.109.88 (talk) 21:44, 2 May 2009 (UTC)

199.125.109.88 There are many textbooks and weblinks saying contradictory things about centrifugal force. The way I was taught it in physics was that centrifugal force does not exist. A circular motion example was given, and it was pointed out that all that was needed was a centripetal force to keep the object in circular motion. However, in applied maths I was taught planetary orbital theory where I learned about the radial equation which includes both inward gravity (the centripetal force) and also an inverse cube law repulsive centrifugal force whose value is independent of gravity. This second order differential equation solves to a hyperbola, a parabola, or an ellipse depending on the relative values of the centrifugal force and the centripetal force. I learned that 30 years ago, but I only learned yesterday that that was Leibniz's approach in the 17th century. Apparently Newton's approach to centrifugal force conformed to Leibniz's approach up until the year 1681. However, Newton and Leibniz had a notorious animosity towards each other over the issue of who invented calculus. When Newton saw Leibniz's radial central force equation, he objected to it. Newton claimed that his 3rd law of motion means that the centrifugal force is always equal and opposite to the centripetal force. So not only did Newton contradict Leibniz, but he also contradicted his own earlier writings on the subject. One of the two must be wrong, and I am of the opinion that Newton's application of his 3rd law to centrifugal force v. centripetal force is quite wrong, and that he only came out with that nonsense in spite of Leibniz.

That Newtonian approach was in some 1960's textbooks. It was in the 1961 Nelkon & Parker 'Advanced Level Physics'. It was used there to explain the centrifuge machine. Yet in the 1971 Nelkon & Parker, centrifugal force had disappeared and the centrifuge was explained using a totally illogical application of centripetal force. Meanwhile, the Leibniz approach to planetary orbits still exists in some classical mechanics textbooks. But the main modern thrust on centrifugal force is neither the Leibniz approach nor the Newtonian approach. The modern approach is that centrifugal force is a fictitious force which is only observable in rotating frames of reference.

I know that you have come here looking for definitive answers. But unfortunately the matter is not that simple. David Tombe (talk) 23:24, 2 May 2009 (UTC)

Alternatively, one can just accept that Newton's 3rd law interpretation is about the reaction force to centripetal force, and that Leibniz's equation is just the fictitious force in the 1D system along the line to the planet, and neither one is incorrect. Dicklyon (talk) 00:39, 3 May 2009 (UTC)

By transforming the problem to 1-D and then further interpreting ddot r as an acceleration (ddot any variable is OK as an acceleration in any 1D problem) one is free to interpret the remaining terms as 1-D forces. However, to take the one-D v/r term and call it the "centrifugal force" is like calling monopoly players businessmen. There is no centrifugal force in any one-D motion. The "velocity" parameter has no interpretation in the one-D motion (it is the transverse velocity from polar coordinates and has no interpretation in 1-D). All intuitive value of the term "centrifugal force" has vanished entirely, and in its place we have introduced confused language very prone to being dragged out the one-D context and applied where it has no bearing. I don't think this peripheral, confusing abuse of language deserves any presence in this article. Brews ohare (talk) 05:37, 3 May 2009 (UTC)

I don't find the language confusing at all; if it was used by Leibniz and Goldstein, then it seems to me that it must have a place here. It's not really any different from the centrifugal force in any other rotating reference frame, it's just a particular frame chosen to make the two-body problem since, and it has only one interesting dimension since the motion in the dimension orthogonal to r is always 0 based on how the frame is chosen. I'm not sure what you mean by v/r here, however; there's no v in this problem. The centrifugal force is express either in terms of the constant angular momentum L or the rate of change of the angle of the system, which is the instantaneous rotation rate (and the fact that the rotation rate is changing gets taken care of by the Euler and Coriolis forces cancelling, which obviously must happen, as the frame is chosen such that the body never moves off the r axis). Dicklyon (talk) 06:31, 3 May 2009 (UTC)

Dick, you're starting to behave a bit like Newton himself. Brews is absolutely correct on this point. We are not dealing with a 1-D problem. You have been continually twisting what Goldstein said. Goldstein said that when we write the radial planetary orbital equation as per 3-12, with the centrifugal force written in the inverse cube law form, then the equation is the same as that which arises in the equivalent 1-D problem.

The fact is that Newton twisted Leibniz's formulation. Newton's interpretation is only partially correct. It is correct in that in the special case of circular motion, the centrifugal force is equal and opposite to the centripetal force. But it is incorrect in that the two are not an action-reaction pair as Newton claims. And it is incorrect in that the two are not equal in general as Newton claims. The two viewpoints are incompatible.

You had no reason to delete my historical outline of this dispute on the reactive centrifugal force page. You are clearly trying to push a point of view. You are trying to superimpose all the business about rotating frames and fictitious forces on top of the Leibniz approach which Goldstein uses. Goldstein never talks about fictitious forces or rotating frames of reference, and you are actively trying to keep the Leibniz approach off the main pages. Your edits on the reactive centrifugal force page are wrong, but of course you can depend on Wolfkeeper to back you up. It's hardly a satisfactory way to write an encyclopaedia article. David Tombe (talk) 12:48, 3 May 2009 (UTC)

David, since you're still very confused about what's a coordinate system effect and what's a rotation effect and how to interpret r double dot in the two systems, here is a book that explains that issue very clearly. I'm sure whether to be flattered or insulted by being compared to Newton, but really, I'm just a wikipedia editor here, and POV pushing is exactly what I'm trying to resist by moving us to where the different points of view can be integrated, compared, and constrasted; however, I don't think your POV is among those, since you are a total outlier with respect to all sources and other editors. Dicklyon (talk) 18:43, 3 May 2009 (UTC)

Dick, my point of view is the Goldstein/Leibniz point of view. I am advocating this equation as being the single equation which unites the entire topic of centrifugal force,

${\displaystyle {\ddot {r}}=-G(M+m)/r^{2}+l^{2}/r^{3}}$

You have been consistently trying to misrepresent my position. You have been falsely alleging that I am pushing some kind of original research, and you have been continually misrepresenting what is written in Goldstein. You have consistently been claiming that equation 3-11/3-12, which is the equation that I have just written above, is a 1-D equation.

When I say that you are behaving as badly as Isaac Newton, I mean it in the sense that you are trying to undermine the Leibniz approach. The Leibniz approach is that a planetary orbit is the consequence of an inward inverse square law force of gravity acting in tandem with an outward inverse cube law centrifugal force, and the two forces are totally independent of each other and not necessarily equal in magnitude.

Isaac Newton tried to sabotage the Leibniz approach by introducing the nonsene idea that the centripetal force and the centrifugal force are an action-reaction pair, and that they are equal and opposite. That approach was found in textbooks right up until the 1960's. It was wrong, but when it was removed, it was replaced by something even worse. The appraoch which is found in most modern textbooks today is that centrifugal force is a fictitious force which is only found in rotating frames of reference. But there is absolutely no need to strap a rotating frame of reference around a situation.

Now that you have discovered the Leibniz approach via Goldstein, you have been trying to corrupt it by introducing concepts from the modern approach and imposing them on top of the Leibniz approach. You are not confused and neither am I. But you seem to have a vested interest in misrepresenting the Leibniz approach. In that respect, you are as bad as Isaac Newton. David Tombe (talk) 19:00, 3 May 2009 (UTC)

Actually, I quite like Leibniz's approach, and Goldstein's, and I can see why you like it, too. But your interpretation of it is twisted, as the book I just linked makes clear. I have no vested interest in any approach, which is why I've been trying to argue that we present them all together. Dicklyon (talk) 20:14, 3 May 2009 (UTC)

Dick, can you please explain exactly in what respect I am twisting Leibniz's approach? There are actually at least three approaches to this topic.

(1) The Newtonian approach. It is partially correct but it is also badly flawed. It corrupts the Leibniz approach by the wrongful superimposition of Newton's 3rd law of motion, totally out of context. The Newtonian approach prevailed in physics textbooks up until about the 1960's. I can give you a classic example. Nelkon & Parker 'Advanced Level Physics' used it in the 1961 edition to explain the centrifuge. It was dropped by the 1971 revision. The Newtonian approach is effectively covered in the wiki article entitled reactive centrifugal force. But it is not a different topic. It is merely a blinkered view of the single topic of centrifugal force which came about because of Newton's notorious resentment of Leibniz.

(2) The modern texbook approach regarding fictitious forces and rotating frames of reference. This approach is just about tolerable so long as we are dealing with co-rotating objects. But why bother childishly strapping a rotating frame of reference around the problem? It is totally unnecessary. Then when this modern approach is extrapolated to situations in which the objects in the rotating frame are not co-rotating, it becomes a total nonsense in which the Coriolis force swings into the radial direction.

(3) There is the Leibniz approach which Newton tried to suppress. It is the approach used by Goldstein. It doesn't involve rotating frames of reference or fictititious forces. It is clearly the best approach in my opinion and this entire edit war has been due to persistant attempts by everybody but myself to keep that approach off these pages. At first they tried to say that the Leibniz approach was my original research. That's because they obviously hadn't heard of it before. They pulled out all stops to keep it off these pages. They endlessly tried to wheel in Cartesian coordinates in order to mask the centrifugal force term. FyzixFighter even hid the term inside a single vector box for radial acceleration. More recently, FyzixFighter blatantly tried to turn the centrifugal force into a centripetal force. Did he think that everybody here would be too stupid to know otherwise? At any rate, he knew he was playing to a crowd that were hostile to my attempts to introduce any approach that exposed the 'rotating frames' approach for what it is. He knew he could count on majority support. Fortunately you and Brews spotted that distortion. But nevertheless, you are now behaving as badly as Isaac Newton. You understand the Leibniz approach but you are trying to distort it. You are trying to corrupt it with nonsense concepts from (2). You clearly don't want a clean version of the Leibniz approach to appear on these pages, and you know that you have got majority support from a crowd who don't even understand the approach.

When the high school level textbooks dropped the Newtonian approach, they replaced it with an arrogant attitude that centrifugal force doesn't exist at all. They attempted to explain centrifugal force effects in terms of centripetal force which is in the complete opposite direction. Hence the situation in the literature is a shambles. That's why we see confused editors like anonymous 199.125.109.88 above.

As it stands now, wikipedia is compounding that confusing by having split the article into two different approaches under the pretext that these are two different centrifugal forces. In fact they are just two different rubbish approaches to the topic. One is in vogue right now and the other went out in the 60's. And this two year edit war has been caused by the fact that a crowd have ganged up to ensure that the 3rd way, which is the Leibniz way, does not appear on these pages. You, who should know better, are part of this. Yesterday, you erased a history section which I inserted at reactive centrifugal force. You claimed that it was my original point of view. It wasn't. It was a point of view copied out of a source which you had actually kindly provided the day before here. But obviously on reflection, you don't want that little aspect of history to be exposed.

Here is a more detailed reference giving Leibniz's position David Tombe (talk) 00:38, 5 May 2009 (UTC)

The more I read about Leibniz's approach, the harder it appears to be to describe it in terms of modern physics. I wonder how the first book I cited got to the equation they presented, corresponding to Goldstein's. If you want to know do I regret starting you down this Leibniz path, yes, I do. Dicklyon (talk) 05:56, 5 May 2009 (UTC)

As to your description of a 3-way POV split, I see it this way: 1 is just Newton's second law; not very interesting, but not incorrect; we have the reactive centrifugal force article on it; 2 is the way all of modern physics treats centrifugal force as a fictitious force in a rotating frame, in which in combination with Coriolis force things work out correctly; 3 is a mixup of 2 with David's idiosyncratic interpretations. And FyzixFighter was not wrong, it turns out, in his presentation of Taylor -- it just took me a while to interpret the symbol soup right with reference to Taylor; in the inertial frame, the term corresponding to centrifugal force does indeed show up as a centripetal acceleration; it is correct that it's in the opposite direction of the centrifugal force, as it has very different roles in the different frames, as the new short article section clarifies. Try actually reading Taylor... Dicklyon (talk) 07:01, 5 May 2009 (UTC)

With respect to the "arrogant attitude that centrifugal force doesn't exist at all", that's nonsense; most physics writers are not arrogant, and most do not say that centrifugal force doesn't exist. You need to learn the different between being "fictitious" and not existing, and look again at who's being arrogant by rejecting all the learning of the last few hundred years. Dicklyon (talk) 07:05, 5 May 2009 (UTC)

Dick, first of all, FyzixFighter was very wrong. The centrifugal force is never the centripetal force no matter what side of the equation we write it on. Secondly, Goldstein uses the Leibniz equation. See equation 3-12 in Goldstein, and that's the way I did it in my old applied maths notes even before I ever saw a Goldstein. I didn't use Goldstein until the next year when I did gyroscopes and Lagrangian. And thirdly, the Leibniz method does not correspond to the rotating frames of reference method. In the Goldstein/Leibniz approach, the Coriolis force is always in the transverse direction. In the rotating frames approach, the Coriolis force has become loose and swings around like a weather cock on a pole.

There are clearly three approaches to this topic. Newton's approach is wrong because it equates centripetal force to centrifugal force under the terms of his third law of motion. But we know that in planetary orbits, the centripetal force and the centrifugal force both act on the same object and that they are not in general equal. You know that already because you have acknowledged it in your edits. Hence, the Newton approach is one aproach, and it is covered in wikipedia by reactive centrifugal force. It disappeared from the textbooks in the 1960's. The Leibniz approach is a different approach, and you should know that there was intense animosity between Newton and Leibniz over the priority in calculus. That is why Newton felt he had to twist Leibniz's approach, because the evidence is that Newton had an earlier stance on centrifugal force which conformed to the Leibniz approach. Then there is the modern rotating frames of reference approach. That is three different approaches. Last year Brews got the idea that the Leibniz approach was a 'polar coordinates' approach. Hence all the unnecessary extra details about polar coordinates in the article. David Tombe (talk) 11:39, 5 May 2009 (UTC)

If you'll read the new section, and follow up by reading the linked cited sources, you'll see exactly how to understand how a term that's a centripetal acceleration due to gravity in one (inertial) frame morphs to a centrifugal force fighting gravity in another (rotating) frame. There's no mystery here, and no opinions or mistakes, just stuff from sources. You'll be able to see where FyzixFighter was quoting Taylor, and how it's not wrong, but a simple derivation from Newton's law, which is in complete accord with Goldstein's method. Dicklyon (talk) 15:40, 5 May 2009 (UTC)

No Dick, Never. The radial equation has both a centrifugal term and a centripetal term. They may be equal in magnitude in the special case of circular motion, but the two terms are never the same thing no matter what side of the equation they are on. You have lost all hope of making a good article because you don't want to accept that the radial equation tells the entire story. It's all too simple for you. David Tombe (talk) 01:25, 6 May 2009 (UTC)

Shortened planetary section

I took the article from about 73 K bytes to about 64 K by implementing my best cut at the proposed shortened planetary section. I think that by keeping the equations in the form F = ma it's easy to see what's being called a force and what an accleration in the different viewpoints, and it becomes clear that Taylor's "centripetal acceleration" term is the same as the "centrifugal force" term but on the other side in a different frame. That is, the inward acceleration term that (along with zero ${\displaystyle {\ddot {r}}}$) curves the path into a circle is the same as the pseudo-force term on the other side that keeps r constant (in the circular case, for simplicity; but more generally as shown in the equations). I don't see any point in the present article of working out the rest of the details of the planetary orbits, which I presume are covered in the three linked "see also" articles.

My hope is that most of you will be happy with this version, or will see simple ways to improve it. I fully expect one outlier to object, but that I don't care about. Dicklyon (talk) 05:51, 5 May 2009 (UTC)

No Dick, by equating Taylor's centripetal force with centrifugal force, you have made the whole article into a nonsense. The centrifugal force does not even equal the centripetal force in general. David Tombe (talk) 10:54, 5 May 2009 (UTC)

Dick, I've just looked at your edits on the main page. I'll check again, but I can't see any reference to what you say above regarding

and it becomes clear that Taylor's "centripetal acceleration" term is the same as the "centrifugal force" term but on the other side in a different frame. dicklyon

I'll check again. If it's not there, then that is good because it is a totally wrong statement. David Tombe (talk) 11:26, 5 May 2009 (UTC)

Check Taylor; discussion of terms in equations 9.69 and 9.71, comparing the forms of the equations in the inertial and rotating frames; see highlight terms in yellow, plus the words like "fictitious" and "co-rotating" used in a precise meaningful way. Dicklyon (talk) 15:45, 5 May 2009 (UTC)

No Dick, centrifugal force is never centripetal force. David Tombe (talk) 23:41, 5 May 2009 (UTC)

Another great source

Enjoy: . Dicklyon (talk) 16:35, 5 May 2009 (UTC)

On a good day, that's actually linked from the article, it's not at all unusual for physics books to include this kind of stuff, and the cartoonist is a physicist as well. It's very on topic. I would have included it in the article, but the license is incompatible. Linking is allowed in cases where we can't include it.- (User) Wolfkeeper (Talk) 01:43, 6 May 2009 (UTC)

New summary article; close merge and move proposals?

I've created a brief summary-style article at Centrifugal force, which should serve to give a bit of positioning, via the table of the different points on view relevant to these topics, assuming that nearly equal and opposite forces from David and Brews don't drag it in opposite directions until it turns into another bloated POS. I think this makes all the current move and merge proposals moot, but before I remove them, please speak up if you disagree. Dicklyon (talk) 23:27, 5 May 2009 (UTC)

Dick, you've taken on the role of chief organiser of this article and you haven't got a clue about the topic. You are deliberately twisting what Goldstein says. Goldstein says that equation 3-12 is the same equation as occurs in the equivalent 1-D problem. Goldstein does not say that equation 3-12 is a fictitious 1-D equation. You have been told this many times but you are persisting on imposing this falsity into the article. You are deliberately falsifying this article. You have a sympathetic crowd on your side who know very little about the topic. I've reported the matter to Jimbo Wales. If he is happy enough with your collective efforts then so be it.David Tombe (talk) 23:40, 5 May 2009 (UTC)

What? Reported the matter to Jimbo Wales? Sorry, I have to get a chuckle from that. I see that this summary style article needs some work in a few areas, but it is a vast improvement over the existing situation. Now, when a user who has only the vaguest idea what "centrifugal force" means searches the term, they will find something that explains it in a way that is accessible. That, and the elimination of the simple redirect from Centrifugal force to the more disambiguated title, is all I have been advocating. While I don't fully agree with Dicklyon's edits, I applaud his efforts to produce a common sense solution where it is so desperately needed. Wilhelm_meis (talk) 14:17, 6 May 2009 (UTC)

Me too. I'm sure that Jimbo will rush on over and quickly straighten this all out. Top priority for the one and only editor for all things most important to get right. However, as I see it, you have an object moving in a non-linear path and you want to know the force acting on it to make it move in such a path. Why do you need three articles to describe it? I really don't care what reference frame you are in, it is still the same force. Anyone with any knowledge of physics knows that it would go in a straight line unless a force was pulling it in which direction? Well that would be toward the axis, and not away from the axis. Hence it is properly called centripetal force. When you get into non-circular paths, you can add a section in the centripetal force article to cover that, but there is no need for a separate article, and no need to invent a separate term from the one that everyone knows so well. 199.125.109.88 (talk) 17:09, 6 May 2009 (UTC)

You're right that the centripetal force is what makes the object follow a curved path. But in other frames, that's not how it looks: in a rotating frame, there is an additional force, the centrifugal one, and the objet might appear stationary or following some other shape of path, possibly curved outward. And that object also exerts an equal and opposite reactive force, centrifugally on the object that's exerting the centrifugal force on it. I agree it shouldn't take three articles to describe it; so now we have four, and that's better, since one of them is simple enough to read. Dicklyon (talk) 17:17, 6 May 2009 (UTC)

Wilhelm, thanks for your support. FyzixFighter, too (see my talk page). Hearing no objections, I'll go ahead. Dicklyon (talk) 17:17, 6 May 2009 (UTC)

Isn't creating a fourth article kind of pointy? 199.125.109.88 (talk) 17:22, 6 May 2009 (UTC)

See WP:SUMMARY for the guideline justification. Dicklyon (talk) 17:33, 6 May 2009 (UTC)

Wilhelm-meis, The reason why I went to Jimbo Wales was because all efforts to do the very thing that you are now advocating have been consistently thwarted. Just like yourself, I have been advocating a single article. I have been advocating a unified, shortened, and simplified article. I have explained to all here, in a few lines, exactly what centrifugal force is. It is an outward inverse cube law repulsive force which is induced by rotation. It appears in the planetary orbital equation alongside the centripetal force of gravity, and the two forces are not in general equal and opposite. They operate in tandem to produce hyperbolic, elliptical, or parabolic orbits.

I have been accused of original research in this respect, but the equation in question is found at 3-12 in Goldstein's 'Classical Mechanics'. It is also the method which was used by Gottfried Leibniz in the 17th century . Dicklyon has been trying to obfuscate this simplicity by introducing irrelevant concepts such as rotating frames of reference, equivalent 1-D problems, and fictitious forces. We now have an anonymous 199.125.109.88 who hasn't got the first clue about the subject and who is trying to tell us all that centrifugal force is the same thing as centripetal force, and he has now even got centrifugal force directed to centripetal force, and nobody has done anything about it. Everybody is being so polite to him. The situation is going from bad to worse. I can't see how you can have noticed any improvement as you claim. Administrator intervention is badly needed here.

If you believe that there should be a single unified article on centrifugal force, then let's see you do it. Let's see you put your money where your mouth is. I can't do it because it would be instantly reverted. And as regards your applauses for dicklyon's efforts to reach a common sense solution, I think that you need to open your eyes a bit more. A common sense solution would be one single article detailing the three existing approaches to the topic in summary fashion, because there is not that much that needs to be said about each approach. I could even write a short summary for the two approaches that I disagree with.

And now I've just seen that you have awarded a merit to dicklyon for his common sense approach. It's becoming like Alison Wonderland. Dicklyon actually removed my edit about the Leibniz approach from the disambiguation page. Where was the common sense there? There is far too much bonding and alliances going on here for it ever to be possible to get a sensible article. I can see that it will get alot worse yet. David Tombe (talk) 19:25, 6 May 2009 (UTC)

Yes, Alison Wonderland; that's me alot. Dicklyon (talk) 03:50, 7 May 2009 (UTC)

Indeed I did applaud Dicklyon's sensible, good-faith efforts to improve the readability of WP's coverage of "Centrifugal force" and not merely advance a particular point of view. I applaud the good-faith efforts of other editors with whom I just as frequently disagree. It's part of civility and it helps us build consensus when we identify the good ideas that we can agree on, and act on them. I think this article and this talk page have suffered precisely because of the inability of several editors to find common ground and build consensus. Several editors seem to be more interested in advancing a particular view of some aspect or another of the subject, rather than working together to produce a more readable article. The summary-style article is a good model that is frequently encouraged on Misplaced Pages, and in this case it may be just the thing to get some of the other editors on board with building a better article. I hope so, and in any case he acted on it boldly, decisively, in good faith and to fairly good effect. I hope we can all get behind this and make it an accurate, well-rounded, and easily readable summary-style article. In this case, I do think four articles is better than three, and quite possibly better than one. I just hope we can all set aside the personal attacks and accusations of confusion or bad faith. Wilhelm_meis (talk) 07:50, 7 May 2009 (UTC)

Wilhelm, since you don't fully agree with my edits, I hope that means I'll be seeing some improvements from you. And big thanks for the barnstar.

I think maybe we should also take the "Development of the modern conception of centrifugal force" section out of rotating frame article, make a whole new article on this interesting history, and put a short summary of it into centrifugal force. Opinions, anybody? Dicklyon (talk) 03:50, 7 May 2009 (UTC)

Wilhelm, Yes, I've been pushing a point of view. You should be taking a closer look at the collective efforts which have been going on to totally suppress that point of view. I think that we have all clearly identified four points of view on this subject. Any final article will therefore have to treat all four points of view. These are,

(1) The Leibniz approach. Centrifugal force is a real outward force induced by the actual circulation of an object. It obeys an inverse cube law and it is not in general equal to any inward centripetal force which may or may not be acting. This is the approach which is used to solve planetary orbital problems and it is found in Herbert Goldstein's 'Classical Mechanics' (1950) which is a gold standard university textbook. It was somewhat tampered with in the 2002 revision, such as to water down the Leibniz approach. The Leibniz approach is the only approach which I support.

(2) The Newton approach. Centrifugal force is real, and it is equal and opposite to the centripetal force. This approach appeared in textbooks up until the 1960's. Nelkon & Parker 'Advanced Level Physics' is a clear cut case of a high school textbook which used this approach and then dropped it in the 1970's. This approach is wrong in my opinion because centrifugal force is not always equal to the centripetal force, and it is not a reaction to the centripetal force. Neither can the two be an action-reaction pair, because the two forces act on the same object.

(3) The rotating frames transformation approach. This possibly originates with Gaspard-Gustave Coriolis in 1835. It is clearly the most common approach in modern textbooks. It considers that the centrifugal force and the Coriolis force are fictitious forces that can only be observed from a rotating frame of reference. I do not support this approach because the rotating frames are unnecessary and the maths has been set loose from the physical realities.

(4) Those that once adopted the Newtonian approach at (2), often replaced it with a new attitide in which centrifugal force doesn't exist. They would restrict their demonstrations to the special case of circular motion and point out how a centripetal force causes the straight line motion to curve into circular motion, and that as such, no other forces need to be involved. Hence there is no such thing as centrifugal force. I totally disagree with this point of view as it totally ignores the already existing outward centrifugal force relative to the origin, which obeys an inverse cube law relationship as per the Leibniz approach. David Tombe (talk) 12:08, 7 May 2009 (UTC)

Recent revisions to Planetary Motion section

I find that recent editorial changes to this section are an improvement. I made some minor additions. Brews ohare (talk) 06:24, 7 May 2009 (UTC)

I just reverted your latest about instantaneously co-rotating, as I believe that it meant rotating at fixed rate, only co-rotating at one instant. In that case, the Euler force is zero and there's a Coriolis force that accelerates the object to move tangentially. But if you let the frame be totally co-rotating, not just at an instant, then the non-uniform rate of rotation induces an Euler force to cancel the Coriolis force, so there's no tangential acceleration, as indeed must be the case if you're co-rotating. At least, that's how I read the sources. You agree? Dicklyon (talk) 06:53, 7 May 2009 (UTC)

Dick and Brews, As regards a co-rotating frame of reference for planetary orbits in which the angular velocity is not constant, I personally can't think of a more cumbersome and unnecessary concept. At any rate, since you have both chosen to entertain the concept, I might as well put a few facts straight. The Coriolis force and the force which you call the Euler force always cancel mathematically. I think that you both realize that. It is the law of conservation of angular momentum. However, they do not physically cancel. This may be a hard fact to grasp, but it is a reality. The Coriolis force can be observed in all non-circular planetary orbits, all vortex phenomena such as cyclones and small whirlpools, and also when a man who is sitting on a rotating stool moves his arms in and out. The Coriolis force is the observed transverse deflection of any radial motion. It is a force which changes the direction of an object, but not the speed. On the other hand, the force which you call the Euler force changes the speed of an object but not direction. Both of these forces can be visibly observed, even if they mathematically cancel each other, and they operate in tandem to yield conservation of angular momentum (or Kepler's second law of planetary motion).

Also, I hope that you have both noted that the Coriolis force is firmly fixed in the transverse direction. It does not swing around like a sign post that has become loose at the joints. I blame Gaspard-Gustave Coriolis himself for allowing this appalling state of affairs to creep into modern physics. If you study his original 1835 paper, you will see that he advocated two supplementary forces for rotating frames. The first was clearly the centrifugal force which he saw as being a force which opposes the applied (centripetal) force that would be needed to drag an object with the rotating frame. The second force was what he called the 'compound centrifugal force'. It was twice the magnitude of the centrifugal force, and Coriolis deduced its existence purely from examining mathematical transformation equations. That's when the 'compound centrifugal force' was first let off the hook and allowed to swing like a weather cock. Many years later, the compound centrifugal force 2mv×ω was given the name Coriolis Force in his honour. Coriolis should have looked more closely at his first category of supplemenatry forces and considered the case of a constrained co-rotating radial motion, such as a marble rolling radially along a groove on a rotating platform. He would have observed the induction of two equal an opposite transverse forces. One of these is the very 'compound centrifugal force' which he identified in its mathematical form and slotted into category 2. The other transverse force is what you guys call the Euler force, and it would cause the rotating platform to either angularly accelerate, or angularly decelerate, according to whether the marble was rolling in or out. Coriolis himself hence allowed the modern Coriolis force to become divorced from conservation of angular momentum, and to become linked to the inertial effects in a rotating frame of reference. And the linkage between the latter and the rotating frame transformation equations is a total shambles in modern textbooks. David Tombe (talk) 11:46, 7 May 2009 (UTC)

Induced by transverse motion?

David put "the centrifugal force, a force component induced by the transverse motion" where previously we had "induced by the rotating frame of reference;" with edit summary "this is an example of the distortion that has been going on. Frames of reference are not involved in the Leibniz approach. Goldstein doesn't mention them". While I agree that Leibniz didn't get there that way, and Goldstein didn't say so explicitly, it's very unclear to me what he means by "induced by the transverse motion;" is there a source that explains centrifugal force in those terms?

I reviewed Goldstein on his; he gets to the F=ma like the one in our article, from Lagrangians, but interprets it the same way, with the central force (e.g. gravity) being the only term in "the force along r" (at his 3.11) and says nothing yet about centrifugal force; he has the centripetal acceleration term in the "a" side, but doesn't call it anything. Later, in his section "The equivalent one-dimensional problem" he has modified the force by adding "the familiar centrifugal force" term, for the "fictitious one-dimensional problem", which is the same as the r coordinate in the co-rotating frame, as I thought was obvious, and which the other sources, and newer editions of Goldstein, make more explicit. This term is "induced" there to make the F=ma work out in this rotating frame of reference, whether he invokes those words or not.

I also just noticed, David, that if you go back to pages 24-25 in your 1950 Goldstein, you find that he commits the same grievous sin that I did, of calling the term in the polar-coordinates equation the "centripetal acceleration". Curiously, the index vectored me there for "centrifugal force"; the index writer must not have seen the difference in these terms. Also, the only other "centrifugal" I can find in the book is where he has "the familiar centrifugal force" term in eq. 4-107, discussing "an observer in the rotating system" and says "the centrifugal force is the only added term in the effective force," p.135-136. So here "effective" is the sum of real and what we nowadays call "fictitious" forces. Obviously, here in Goldstein, it's induced by the rotating frame of reference.

So give it up. Dicklyon (talk) 15:20, 7 May 2009 (UTC)

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