Talk:Centrifugal force (rotating reference frame): Difference between revisions

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	== The condition "does not exist in an inertial frame" doesn't fit the objectives of physics ==

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	] added a comment to an existing post, way at the top of this talk page. I copy ]'s comment here: <br>
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	: The scope of this article extends beyond the first month of high school physics. What high school physics teachers should say is "The centrifugal force does not exist ''in an inertial frame of reference''". But then they would have to explain what a non-inertial frame of reference is, and that is usually saved for the university courses. --] 09:02, 11 January 2007 (UTC)
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	The condition "does not exist in an inertial frame" is blurry, and it does not qualify as a physics statement. Physics is about the entities that are frame-independent. That is: independent from the way we assign numbers to certain states. For example, for temperature there is the scale of Fahrenheit and there is the scale of Celsius. Each scale assigns different numbers to the melting point of ice and the boiling point of water, and this difference is irrelevant for physics considerations. Calculations can be interconverted between units of Fahrenheid and units of Celsius. Likewise, calculations can be interconverted from mapping motion in an inertial coordinate system or a rotating coordinate system. Either way, inertia exists, independent of how a particular motion is mapped. Inertia exists, and when an object is forced into non-inertial motion, the object's inertia manifests itself.
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			== Not to be confused with ==
	This is a matter of principle: the building blocks of physics theories are entities that are independent of the way that motion happens to be mapped.

			There are various warnings not to confuse various forces: ], ], ], ]. There is however no discussion of the distinction between these various phenomenon. --] (]) 20:46, 2 July 2012 (UTC)
	Summary: <br>
	Independent of whether motion is mapped in a inertial coordinate system or in a rotating coordinate system, one can recognize the role that inertia of objects is playing in the physics taking place. What teachers should teach is that inertia exists, and how it plays a part in physics taking place. --] \| ] 13:50, 11 January 2007 (UTC)

			== More properly an effect than a force? ==
	:: Cleonis, you and I have iterated this discussion ad nauseam already on my talk page and in other places. I agree with everything that you say above. Fictitious forces do not exist in the sense of fundamental interactions, and often physics teachers don't explain inertia in the best way.
	:: However, the question was whether the page should be replaced with a short text referring readers to the centripetal force page, because of what the anon's physics teacher had said. This I disagree with. The ''concept'' of fictitious forces does exist, as a useful mathematical tool, when dealing with non-inertial reference frames. As an analogy, ]s do not exist from a certain philosophical perspective, but the ''concept'' of negative numbers is very useful in mathematics, and hence it is a good idea to keep that page as it is rather than replacing it with a text stating that they don't exist, and then pointing readers to the ]s page. The same is true for this page. --] 12:21, 12 January 2007 (UTC)

			I suspect that the lead would be better if reworked à la N.M.J. Woodhouse, who writes (p. 7) in his ''Special Relativity'' (Springer-Verlag, 2003),
	:::I suppose this relates to ambiguity in the verb 'to exist'. Often in physics a discussion may arise as to whether something actually exists. For example, from a human perspective, we may well get the impression that there is some cold-suction action, where a particular cold actively ''sucks'' warmth away. From a physics point of view, there does not exist an active suction from cold being exerted on warm regions. So I prefer to be very cautious with the verb 'to exist'. If a calculation would be set up in which a fictitious cold-suction-force is applied, I'd still emphasize that no cold-suction force exists. In the case of applying a mathematical tool, there is no need to assert that it "exists" (inviting the ambiguity of that verb), it suffices to assert that the tool is regularly applied, and that it is very useful.
			:"In problems where the rotation matters, for example in the analysis of Foucault's pendulum, it is helpful to treat a terrestrial frame as if it were intertial, but to introduce correction terms, the 'fictitious' centrifugal and Coriolis forces, to take account of the rotation. But these are not real forces, and the frame is not really inertial."
	:::Ambiguity cannot be eliminated entirely, but every opportunity where it is easy to avoid ambiguity should be used. --] \| ] 14:21, 12 January 2007 (UTC)
			Indeed, even ] is a redirect to ''Coriolus effect'', and that article makes it clearer than this one does that the force is only apparent. I'd have just changed it myself, but wondered if there were a good argument for retaining the nonparallelism of treating one of the two forces as though it were somehow less fictitious than the other.—] (]) 20:57, 19 February 2013 (UTC)

			:My two cents here - I think there is a distinction between "effect" and "force" in these instances. My feeling from the literature that I've read is that the effect refers to the apparently anomalous deflection of the path of a particle while the force is the pseudo-force or fictitious force that is introduced to explain the deflection. As for an argument for retaining the nonparallelism, this is what we find in the literature, ie the terms "Coriolis effect" and "Coriolis force" are used with about the same frequency and sometimes it seems inter-changeably. The choice also seems to be dependent on the context - in meteorology we find "Coriolis effect" (and my guess this is true for the everyday person), while in the physics literature "Coriolis force" is more common. I don't think the same can be said for "centrifugal force"/"centrifugal effect". Just to get a general idea of how common the terms occur in the literature I searched for each phrase in google books:
	:::: Heat transfer works just the same with signs reversed. In fact, on the temperature scale which ] originally used, increasing numbers represented colder temperatures. Absolute temperature is a rather recent invention.
			:* Coriolis effect : ~44,500
	:::: One could say that the centrifugal force does not exist in the same sense that "cold" does not exist. But I think you're right in that one probably does best in avoiding the word "exist" altogether. --] 21:38, 13 January 2007 (UTC)
			:* Coriolis force : ~138,000
			:* Centrifugal effect : ~16,700
			:* Centrifugal force : ~1,260,000
			:That's almost two orders of magnitude difference for centrifugal between effect and force, while for Coriolis the two are roughly equal (okay, a factor of about 3 but less than an order of magnitude). So imo I don't care whether the other article is "Coriolis effect" or "Coriolis force", but I strongly favor keeping this one as "centrifugal force" per the usage frequency in the literature. That being said, if the intro needs to be clearer on it being a fictitious force then that should be fixed. --] (]) 05:33, 20 February 2013 (UTC)

			:I agree with FF. If you want it more parallel, go the other way. And I'd avoid the notion of "only apparent", since we already have a well-define notion of "fictitious force" that says exactly what it is. ] (]) 05:49, 20 February 2013 (UTC)
	::::: So do we have a consensus to rewrite or remove all assertions that such-and-such concept does or does not "exist"? ] 00:49, 14 January 2007 (UTC)

			== Acceleration Derivation ==
	:::::: It does seem that there is such a consensus; asserting the usefulness, without using the verb 'to exist'. For the example of heat transfer it means that it would be asserted that what exists (according to our theories) is 'entropy'; heat will flow from the warmest regions to any less warm regions. --] \| ] 11:17, 14 January 2007 (UTC)

			In the derivation section, I'm noticing that the last two lines of equations in the "acceleration" section do not seem to follow from one another. When I evaluate the d/dt(+w x r) term in the next to last line, it does not give the factor of two in front of the Coriolis term. I believe the error is leaving out part of the first derivative operator: that is, in that equation, instead of the operator "d/dt" we should have "d/dt + w x" as the operator. (also see the rotational reference frame wiki page for that derivation, in which the derivation correctly gets the factor of two into the Coriolis term)
	== Centrifugal force in statics ==
			I would just go ahead and add it, except I'm not at all familiar with the proper coding for inserting equations into wikipedia, and am very new here in general <span style="font-size: smaller;" class="autosigned">— Preceding ] comment added by ] (]) 02:13, 6 March 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

			: It is correct. Don't forget that
	I originally created this section about a year ago as part of an attempt to make what the article now describes as "fictitious centrifugal force" its main topic and then explain how in limited cases the "reactive centrifugal force" also makes some sense. It appears that my point was rather poorly made, and that the section has survived to this day mainly because no subsequent editors have felt they understand it well enough to remove it. In the context of how the article looks now, I think the section is confusing and misplaced; I'd like to delete it all. Has anybody secretly grown so fond of it that they would complain if I did? ] 00:46, 14 January 2007 (UTC)
			::<math>\frac{\operatorname{d}\boldsymbol{r}}{\operatorname{d}t}=\left + \boldsymbol{\omega} \times \boldsymbol{r}\ ,</math>
			:and of course likewise
			::<math>\frac{\operatorname{d}}{\operatorname{d}t} \left=\left + \boldsymbol{\omega} \times \left \ ,</math>
			:so that is where the second term comes from.
			:'''Note''' - this derivation could need a source. - ] (]) 12:47, 6 March 2013 (UTC)

			== It's the rotation of the ''direction of the velocity vector'' that matters, not of the frame. ==
	:I think the opening sections already cover what is addressed in the section 'centrifugal force in statics', and that the opening sections do a better job.

			Yep. We have here a misleading article title, and misleading wording that implies that a ''reference frame'''s rotation results in centrifugal force/pseudoforce. Rather, it's the ''centripetal acceleration'' of the frame (or object) that results in such forces. The centripetal acceleration of the frame (stated in an inertial frame) is proportional to the rate of change of the ''direction of the velocity vector'' (also stated in the same inertial frame). Thus, if the rate of rotation of anything matters, it's the rate of rotation of the direction of the velocity vector, ''not'' the rotation rate of the frame.
	:Anyway, the scope of statics is objects that are in equilibrium. To test the load-bearing capacity of a suspension bridge, a large amount of heavy vehicles is parked halfway the length of the span of the bridge. Another part of testing a bridge is to find out whether winds can trigger an oscillation of some parts of the suspension bridge. That is dynamics. Calculations/modeling in statics do not involve inertia, calculations in dynamics do. --] \| ] 11:39, 14 January 2007 (UTC)

			I grant that, in most usual cases (such as ball-on-string), the most common frame is attached to the object (ball) and is also rotating along with the object. The rotation rate of the frame in these cases is the same as the rotation rate of the direction of the velocity vector, ''but that's only incidental''. It's the rate of change of the direction of the velocity vector that makes for the centrifugal forces here. If the frame was still attached to the ball, but was chosen to rotate at twice or three times the rate of the velocity vector, or if it was chosen to not rotate at all, it would not effect the magnitude of the centrifugal force, nor would it effect the actual direction of the centrifugal force. Such an independently-rotating frame would have different ''numbers'' representing the direction of the centrifugal force, but the actual direction (or magnitude) of the centrifugal force at any particular moment would not vary with rotation rate of the frame.
	:: So removed. For what it's worth, the intended relevance of "statics" was a situation where one wants to design a complex system that rotates (i.e. where all the constituent parts are supposed to follow the same constant rigid rotation) such as a centrifuge or a flywheel, and we must find out whether the various contact forces and internal stresses will suffice to supply the necessary centripetal forces. This can be done most easily in a rotating frame where nothing moves and the various shortcuts of statics are thus available, if only we add in artificial loads from the centrifugal force. ] 01:11, 17 January 2007 (UTC)

			We should not muddle-together the ''movement'' of a frame (such as in a circle about a point) with ''rotation'' of the frame. They are two different things that can be independent. If we don't keep that in mind, it leads to fallacies.
	::: Of course, in the case of rotation of solid bodies the analysis reduces to statics.

			] (]) 17:32, 31 May 2015 (UTC)
	::: Interestingly, it's quite rare that the analysis reduces to the statics case. For example, in the case of helicopter blades, a major concern is that when the rotating helicopter blade bends upwards, it's center of gravity moves closer to the rotation axis, resulting in an increase of the blade's velocity. More blade velocity gives more lift, which tends to increase the upward bending. When the frequency of the blades flapping up and down coincides with the rotation rate, this mechanism of self-reinforcing vibration can cause the helicopter blades to shatter. Rotor designs must incorporate dampening to dissipate the energy of vibrations. Any device with rotating parts is prone to developing self-reinforcing vibrations.
	::: Generally, what needs to be modeled is rotation with a variable rate of rotation. When a calculation is set up for helicopter blades with an oscillating rotation rate due to vibration, the coordinate system that will be used is a coordinate system with a ''constant'' rotation rate, hence the centrifugal term will be constant. The amount of reactive centrifugal force will oscillate, since the rotation rate of the blade oscillates. Whenever rotation is accompanied by vibration, the centrifugal term and the reactive centrifugal force are distinct.
	::: Summerizing: <br> Generally in using rotating coordinate systems, the centrifugal term and the reactive centrifugal force do not coincide, they coincide only when the rotating body can be considered vibration-free. --] \| ] 02:14, 17 January 2007 (UTC)

	== Note 8 ==

	I'm really not seeing the relevance of this reference, even applied inline. What does it have to do with centrifugal force? Particularly odd with the comment that reactive centrifugal force can 'even smash DVDs'. Vandalism/SPAM? Or am I missing something? ] 23:20, 10 February 2007 (UTC)

	: There is a single line in there that if a DVD should spin fast enough, the disk will shatter. So the reference is relevant, but the relevant line is hard to find, and that makes it a lousy reference. In addition, I don't see that the article quite counts as a reliable source. My advice is to remove the DVD shattering phrase and the reference. --] \| ] 05:16, 11 February 2007 (UTC)

	:: I agree. The DVD shattering phrase seems to try to convince a reluctant reader that the "reactive" centrifugal force is a real force. This is problematic for two reasons. First, nobody disputes the reality of the reaction force. (Some of us do hold that it is not conceptually ''interesting'', but that is a different question). Second, it is not NPOV, by the rule of thumb is that if you find yourself trying to ''convince'' an imagined reader who you think would not accept a plain statement of fact, you're pushing a POV. An encyclopedia should not aim to stuff truth down the reader's throat; it should simply state plainly that such-and-such is the accepted truth, and then leave the reader to wallow in his delusions if he so chooses. ] 16:55, 11 February 2007 (UTC)
	::: So removed. ] 21:21, 13 February 2007 (UTC)

	== Change article name ==
	Since Cintrifugal force doesn't exist i think we should just move the article to be called centripital or w.e

	: No. Read the section entitled "Confusion and misconceptions". --] 12:14, 17 March 2007 (UTC)

	To change the name of the article is an absolutely ludicrous suggestion. The argument has been over whether or not the centrifugal force is real or fictitious. Even both sides in the argument are agreed that it exists one way or the other. And both sides in the argument are in total agreement about the fact that whatever centrifugal force is, it is most certainly not the same thing as centripetal force. David Tombe 15th April 2007 (] 08:38, 15 April 2007 (UTC))

	== Third Paragragh edit ==

	I removed a line which read as "Note that this real centrifugal force does not appear until the person touches the body of the car." This is erroneous, as the car exerts this force on the person whether or not they are touching the body of the car.
	: You're wrong. First, the force this sentence speaks about is not one that the car exerts on the passenger, it is the force with with the passenger pushes the car door outwards. Second, this force does only appear once the passenger makes contact with the car door. (We ain't having no action at a distance here). You may not want to ''call'' this force a "centrifugal force", and you'll be very welcome not to; I don't either. But it seems to be fact that some people do call it a centrifugal force; consensus ended up being that this meaning of the word should be explained in the article too. I will revert. –] 19:45, 30 April 2007 (UTC)
	I'm not sure the line: "In this case the centrifugal force is canceled by the centripetal force, and the net force is zero, thus the person does not accelerate with respect to the car." is particularly well chosen. In what sense are these forces "canceled"? You state correctly that the "centripetal" force is the force of the door on the passenger, and that there is a force that some refer to as "centrifugal", and that this is actually the (reaction) force of the passenger on the door of the car. These are simply the Newton's 3rd Law action and reaction pair of forces. To say they "cancel" is very misleading! They act on '''different objects'''. They do not cancel. The "net" force you refer to would need to be the result of two or more forces on the '''same''' object. ] 12:22, 30 May 2007 (UTC)
	: You're right: that sentence is wrong when speaking about the reaction force. I have removed it. –] 15:05, 31 May 2007 (UTC)

	== Confusion and misconceptions POV ==
	The tone and some of the content of this section should be kept for the talk page. Not everyone teaching or learning in a high/secondary school lacks an understanding of what centrifugal force is. This is an encyclopaedia not a gossip column, you don't want to insult future contributors or readers. If this section really needs to stay then where are the referenced school graduate statistics to back it up? ] 08:29, 27 August 2007 (UTC)
	: I can see that the text could be misunderstood as meaning that the teachers lacked understanding. What it was meant to say was that teachers (who presumably do understand centrifugal force and when it is valid to use it) often do not have time to pass on that understanding to their students, simply because rotating frames are not part of what they are supposed to teach. The students in the mid-bracket who are bright enough to understand what they ''are'' taught, but not so good that they'll invent on their own what they ''aren't'', will be left with a half-truth, not because the teacher is ignorant of the full truth, but because the half-truth is all the curriculum requires them to learn.
	: I have tried to edit the sentence to prevent the misunderstanding. Does the current form address your complaint? –] 21:19, 13 September 2007 (UTC)

	== I blanked the derivation ==

	I because it didn't add any information beyond what was in the previous section, I know for a fact that the large number of equations are imposing and dissuade some readers, and it was very long. Misplaced Pages is ] not a how-to manual. If there was actually some useful information imparted beyond an algebra lesson only tangentially related to the subject of the article, then I will apologize. But there wasn't as far as I could see. ←] 17:31, 12 September 2007 (UTC)

	: Well done! --] 17:23, 13 September 2007 (UTC)

	== Cartoon ==

	I must admit, I would ''love'' to negotiate a license to get this in the article: ; but I'm sure somebody would take it out on tone reasons or something. Lots of physics text books have little cartoons like that in though, so there's quite a bit of precedent.] 22:13, 1 October 2007 (UTC)

	: I'd support the addition. The motivation for keeping it in the article (except for the fact that it is funny) is that it illustrates the debate on the "existence" of the centrifugal force in a good way. (Because it comes from an external source, it is in a way "evidence" that the debate exists. - The artist knew that people would recognize the discussion. If somebody had drawn the same cartoon after reading the[REDACTED] article, for the explicit purpouse of inclusion in the article, I'd be opposed.) See also ] --] 08:01, 2 October 2007 (UTC)

	:: I love it - it's nicely pointing at the debate, without taking position. Great! Perhaps they will agree it to be included with mention of the source? That's kind of publicity for that site (allowed, right?) ] 21:01, 2 October 2007 (UTC)

	You can ask at ] - I bet he will relicense it without the -NC in the CC license so we can use it. ] 04:13, 3 October 2007 (UTC)

	== Non-rotating non-uniform coordinate system ==

	I removed the following subsection (recently added in good faith by ]) from the article:
	: If a problem exhibits polar, spherical or cylindrical symmetry, a polar, spherical or cylindrical coordinate system can be used. These are "rotating reference frames" in themselves, even if nothing is physically rotating. For instance applying spherical coordinates to a system of an object moving around on a non-rotating planet or polar coordinates when addressing planetary orbits will often result in centrifugal forces appearing. The cause is the same as when "attaching" a (in itself inertial) cartesian coordinate system to the surface of a rotating planet or a turning car.
	It is true that one needs correction terms that modify ''coordinate'' accelerations if one uses non-uniform coordinates such as polar coordinates. However, I do not think these corrections can meaningfully be described as "centrifugal forces". For example, if you place a free particle at rest ''anywhere'' in a non-rotating polar coordinate system, it will stay at rest, i.e. its coordinate acceleration (as well as its true acceleration) will be 0. If there was a centrifugal force, the particle should have an acceleration away from the axis, but it hasn't.

	It ''may'' be meaningful to describe the corrections more generally as ]s, but I am not sure that this is actually a common way of handling the problem. Some sources would be necessary for this. –] 15:11, 16 November 2007 (UTC)
	::If we formulate it like this. In cartesian coordinates we may have
	:::<math>\frac{d^2\mathbf{r}}{dt^2} =\frac{GMm}{r^2} \hat r</math>
	::imagining that "m" is just a test-particle so "M" can be fixed in the Origo. Now if we instead want to use "r" as the radial component in polar coordinates instead we get
	:::<math>\frac{d^2r}{dt^2} = \frac{GMm}{r^2} - r\dot \theta^2</math>
	::It is the extra fictitious force in the last equation I would like to refer to as "centrifugal". Perhaps it has another defined name? Do anyone know what the proper name is?-- ] (]) 17:40, 16 November 2007 (UTC)
	:::Perhaps it could be reinserted formulated alomg these lines?-- ] (]) 17:40, 16 November 2007 (UTC)

	== Overthinking it ==

	A lot of this article does not make sense. The concept of centrifugal force only has relevance in a rotating frame of reference, whether used in calculations or empirical observations. An often quoted example used to prove that centrifugal force "is fictitious" is that of spinning with an object held at the end of a string; the hand exerts a force on the string which holds the object in, so the object must be exerting an equal and opposite force on the hand via the string. But somehow that opposing force isn't real, or is qualified by stating it is a reaction force or something like that.

	Trying to make this fit it into an inertial frame of reference is subverting the physics behind the phenomenon. When describing the force it is fixed and motionless; in a fixed frame of reference the force vector would be spinning, which is at odds with the description of the physical experience. The object opposing the force (the hand) is fixed (in a rotating frame); if it were fixed in a non-rotating frame, then the string would wrap around the hand and the experiment would end. The observer describes a static system, all under rotation. The observer is less likely to think in terms of pulling the object off its inertial straight line and onto a circular path thereby creating a dynamic force (constant in magnitude but varying in direction). This distinction is more than fleeting; if the observer is inside a rotating cylinder then they would have no idea that a fixed frame of reference even existed.

	So if anything, centripetal force is the more obscure 'advanced physics' concept, and trying to wash away the core of the physical experience (the static forces and the obviously rotating frame) as "too advanced" is bound to cause confusion and dissatisfaction. --] (]) 14:43, 18 November 2007 (UTC)

	: I wonder how you can think that a concept that Newton used in relation to inertial reference frames, "has no relevance". It boggles me how anyone can claim that its original and straightforward meaning "is subverting the physics". Also, this article does '''not''' claim that all "centrifugal force is fictitious".
	: Thus I can't make sense of what you are trying to say; and I saw no reference to any specific part of the article. It's not clear what anyone would be deeming "too advanced". If you want to help improving this article, please study the sections that discuss the usage with which you are familiar and propose specific improvements to those sections.
	: ] (]) 16:19, 18 November 2007 (UTC)

	:: I agree that it is hard to tell what Adx's complaint is. He appears to be confused by the fact that the article describes ''two different concepts'', though I cannot see a way to make it clearer in the article that this is going on. We will probably be able to make progress only if Adx points to specific sentences or paragraphs that he thinks are wrong/misleading. –] 17:04, 18 November 2007 (UTC)

	Apologies for pointing the finger of blame at the article, that was not my intention, I don't have a problem with its technical accuracy. My point is that many people will come here wanting to know "why centrifugal force does not exist". Rather than provide a physics lesson, the article could start off by breaking down their experience of the real force they feel while rotating, into the equivalent inertial frame explanation (that Newton invented as a tool to deal with exactly this type of conceptual problem). The inertial frame explanation is less physically relevant because it deals with dynamic force vectors, but it does nicely explain what is happening to the system as a whole. (In other words, an article about centrifugal force not textbook physics, if you see my point.) Nowhere did I say the article claims "all centrifugal force is fictitious", just that it gives no straight answer on this point. By "too advanced" I refer to the section dealing with how the confusion is often ignored in high school physics, where if pressed the final answer will be "just take my word for it, centrifugal force isn't real". That is "subverting the physics", this article does a much better job but it isn't perfect. Perhaps it isn't Misplaced Pages's job to depart from tradition, so feel free to dismiss all this as the idle ramblings of someone who is on a different planet.--] (]) 14:27, 22 November 2007 (UTC)

	==My college professors told me "centrifugal" is not a force==
	And they advised me never to use that term in their classes. As they explained it, the proper term would be "intertia"... i.e. the desire to the rotating mass to continue moving straight ahead. It is only the centripetal force (think string) that keeps it from following its inate inertia.

	That said, I think this article needs a major rewrite to clarify the centrifugal force is not a force. A more proper term is "inertia". - ] (]) 12:55, 10 December 2007 (UTC)

	:Not to be blunt, but your college professors are either (1) wrong, (2) didn't tell you the whole story, or (3) you misunderstood them. Reread the car example discussions in the article (and discuss them with your professors, since it may be helpful for both them and you to figure out how the miscommunication happened). Basically, think about if you turn your car sharply. Your body has a tendency to move outward, which is (as you say) INERTIA, not a "force." People incorrectly call that tendency of your body to move outward a "force," when it is actually just a basic property of matter, namely inertia. That's probably what your professors want you to realize.

	:However, if your body moves outward, hits the door (or window or whatever), and then PUSHES against the door, you are indeed exerting a FORCE on the door. The direction of that force is OUTWARD and is therefore properly termed centrifugal. The door exerts a force back INWARD to hold you from flying out of the car, which is the centripetal force. Or, another way to think of it -- Newton's third law states that forces occur in pairs. So if there is indeed some force pushing inward (centripetal), there must somewhere be a force pushing in the opposite direction (centrifugal). The existence of one implies the existence of the other. HOWEVER, that outward-pushing ("centrifugal") force isn't what causes you to move outward in the car... that's simply inertia. Physics professors and teachers are trying combat the misuse of the term. However, if they say a centrifugal force CAN'T exist, then a centripetal one can't exist either... it would violate Newton's third law. ] (]) 05:02, 12 December 2007 (UTC)

	::You appear to intend to be very blunt yet you say "not to be blunt". That doesn't seem to follow the spirit of wikipedia. My college professors also told us not to use the phrase Centrifugal Force. I trust them more than alot of unreferenced stuff on wikipedia. Not that I don't love wikipedia. But it is what it is. And a physics book it is not. Maybe as a result of this article the newer college physics books will insert a footnote about it. But that is all it would be since it is not needed to do the free body diagrams and calculations. The person sitting in the car never experiences a centrifugal force (unless his big brother the physics student shoves him out the door for arguing pro-centrifugal force rhetoric).] (]) 15:22, 12 December 2007 (UTC)

	:::Thanks Crunchy.

	:::I would love to ask my profs the question, but having graduated that's no longer possible. ----- You are correct that the door is what keeps my body moving in a circle. That is indeed Centripetal force (actually it's the whole car that exerts the force, since the car is all connected as a single piece). However the force that I exert on the door is NOT centrifugal force. False. It is the '''Normal''' force... an opposite reaction to what the car is doing to me. Please don't mis-label things. - ] (]) 19:33, 12 December 2007 (UTC)

	:::: This was first discussed several years ago, and references were presented (they are still present in the article) to the effect that some people who do know what they are talking about do sometimes refer to the reaction to the centripetal force as "centrifugal force". I would agree with you that this is a ''confusing'' usage, but the mission of Misplaced Pages is not to try to spread a better way of thinking than that actually used in the sources.
	:::: However, the more common meaning of "centrifugal force" is a correction term that one must use if (and only if!) one analyses a situation with a rotating coordinate system. Your professors may well have told you not to use the term ''in class'', because you were not supposed to use rotating coordinate systems ''in that class'', and therefore it would be a sign of misunderstanding if you felt the need to include a centrifugal force in your calculations. However, the fact that there are contexts where it is wrong to use a centrifugal force does not imply that it is ''always'' wrong to use a centrifugal force. –] 23:02, 22 December 2007 (UTC)

	::::: Hi, Theaveng. I made the original reply, and I do apologize for being blunt. That said, I still would argue that your response is based on a misconception -- i.e., calling the other force a "normal force" (and saying that is the ONLY term for it) seems to be a way of putting it in "second place" to the centripetal force, which everyone seems to think is the "real" force. My point is simply that you can't have a force by itself. They always come in pairs. And if you have one force pushing or pulling inward (a "centripetal" force), then there MUST be a force pushing or pulling outward. (Yes, they are acting on different objects, but they are both there.) Neither is prior to the other; they can only exist together. Therefore I think it's almost as bad a misunderstanding to emphasize centripetal force alone as it is to get confused about the role of inertia in these situations. I think the common terminology you describe (i.e., using "centripetal" but saying you can't even use the word "centrifugal") is thus misleading. There are often forces that are "center-fleeing," and saying we can't use the word "centrifugal" to describe them because many people don't understand inertia is a bit ridiculous.
	::::: Let me switch examples to make this clear. Say that your average person was taught that there were such things as "normal forces" but they completely misunderstood the term and thought it referred to "normal" as opposed to "special" or "extraordinary." (Thus, "normal" forces were generally always there in a problem, as opposed to the added forces that generally play a role in non-static situations.) Say this misunderstanding was fairly common. (It has occurred in my high-school physics classes when the term is first introduced, despite many clarifications.) Should we abandon the term "normal" and say it can't be used in physics class to refer to a force just because most people use the term incorrectly?? Or should we instead teach that the word "normal" is actually a general mathematical term that has to do with perpendicular relationships?
	::::: So, I really didn't mean to be insulting (apologies Crunchy Numbers). But for the same reason that many people have a pet peeve about using centrifugal force incorrectly to refer to inertia, my pet peeve is people who seem to be intent on stamping out the idea that "centrifugal" forces can exist when in fact they MUST exist whenever centripetal ones do. Etymologically, the word "centrifugal" just means that it's a force going outward away from the center. Why not teach people that they can use such a term to describe actual forces that fit that description rather than banning the word?
	::::: Lastly, Crunchy, I'm sorry, but you're wrong in most cases to say that the person in the car "never experiences a centrifugal force." For example, if I'm holding a cup in my hand as the car goes around the turn, the cup will exert a centrifugal force (outwardly-directed) on my hand. Even if I'm not holding anything, generally I'll at least be wearing clothes which will exert centrifugal forces against me. Even the air molecules in the car will have inertia and will push against me, exerting an outward force that is just as real as the force that the door exerts back on me. Why give only one of these things a special name ("centripetal") and say that all the forces from the cup, my clothes, and the air don't get a special name? Only if I were being rotated naked in a vacuum could you really make the claim that I'm not experiencing centrifugal forces external to myself... and even then, the blood vessels walls, etc. inside my body will be.
	::::: Simply put, from an etymology standpoint, centripetal and centrifugal just refer to different directions. Using nomenclature that privileges forces in one of those directions (while banning the use of the term for the other direction) is inconsistent and leads to further misunderstandings about the operation of Newton's Third Law... at least from my experience teaching in physics classrooms. ] (]) 06:47, 12 January 2008 (UTC)

	:::::: By the way, I also do agree with Henning Makholm's bit about rotating coordinate systems and the usefulness of "centrifugal force" to describe things in such a case. That's a really useful shortcut in certain situations that are more advanced than introductory physics. But, in my view, it isn't really objectionable to say you can't use a term until you understand the situation where it's appropriate, which seems to be your physics professor's take. What I do object to is the system of terminology that results, which strikes me as inconsistent (and somewhat misleading) for inertial frames. So, I just want to be clear that I have no argument with Henning's take on this, though I still object to explanations that ignore the force-pair involved and just focus on inertia and the effects of centripetal acceleration. But, as Henning points out, this has all been discussed at length in the Talk Page archives.... ] (]) 07:45, 12 January 2008 (UTC)

	::::::: The misconception here is that you can't have a force by itself, and that forces always come in pairs. This is only the case in stasis. Unbalanced forces cause an accelleration. Thus from the perspective of outside the car (the inertial reference frame) the unbalanced force of the car door is causing you to accellerate (towards the other door). We say F=MA, i.e. an unbalanced force causes a mass to accelerate. From the perspective of inside the car, an almighty hand of God forces you towards the door and the door pushes back, which is hardly physics, more theology. ] (]) 15:58, 5 March 2008 (UTC)

	:::::::: F=ma describes the acceleration that corresponds to dynamic force equilibrium. For example, if you accelerate a car by pushing it, the car equally pushs back at you as you can easily see and feel: the flesh of your your hands is being deformed by the force with which the car pushes back at you - it is the inertial force (related to "inertial mass") that regulates the acceleration. Should a clarification like that perhaps be included in the text of this article or (with a link from here) in an article about F=ma? ] (]) 21:33, 5 March 2008 (UTC)

	== Wrong interpretation of "Centrifugal force" ==

	I read that there are two types of centrifugal forces :
	".../...1) A real or "reactive" centrifugal force occurs in reaction to a centripetal acceleration acting on a mass. This centrifugal force is equal in magnitude to the centripetal force,.../...
	2) A pseudo or "fictitious" centrifugal force appears when a rotating reference frame is used for analysis./..."

	For the first type, Misplaced Pages gives the following example:
	"Both of the above can be easily observed in action for a passenger riding in a car. If a car swerves around a corner, a passenger's body seems to move towards the outer edge of the car and then pushes against the door..../...However, the force with which the passenger pushes against the door is real. That force is called a reaction force because it results from passive interaction with the car which actively pushes against the body. As it is directed outward, it is a centrifugal force."

	These last sentences are of course wrong. The passenger doesn't push against the car, but the car is turning and the passenger is just going straight forward, due to his inertial mass, with the consequence that the car pushes the passenger. And that force is of course centripetal, not centrifugal! Thus: centrifugal forces still don't exist.
	Only the reaction force on a change of direction of a inertial mass is real. The force of the car on the passenger is real.
	:No, from ], if the car pushes on the passenger, then the passenger also pushes on the car with an equal and opposite force. So there is a real force there.- (]) '''WolfKeeper''' (]) 20:01, 31 January 2008 (UTC)

	What is the origin of the misunderstanding? Probably because at school, the teachers have slammed with a hammer the Laws of Newton in our head. And the famous law Action = Reaction is one of them. If there is a centripetal force, where is then the reaction force? Well, there isn't any. Inertial masses are allergic to changes of direction and velocity. And everything that try obstructing the inertia will exert a force to that inertial mass, inwards, thus centripetally.] (]) 19:52, 31 January 2008 (UTC)

	::Any 'reactionary force' that may appear to occur in this situation is just a component of the velocity of the car around the corner. There is no centrifugal force in this case; I do not understand the concept fully enough to say that it never exists, but in this case it most certainly does not. If I could draw a diagram it would show that there is a centripetal force, towards the middle of the corner (if we treat it as a circle), and the velocity of the car at any given time, forward. The 'centrifugal' force is actually felt from a combination of these two forces acting upon the car and, transitivley, on the people inside. 17:48, 7 February 2008 <small>—Preceding ] comment added by ] (]) </small><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->

	== some possible additions, moved from intro ==

	The following was added to the intro in a way that made the intro less coherent (it even introduced a third bullet point where only two bullets belong):

	''Centripetal acceleration is the term for the continuous change in linear velocity as a point curves about the axis of rotation rather than flying off the body tangentially. ''

	* ''When an external force angularly accelerates a body that remains intact, an equal and opposite tangential force is exerted by the rotating object in accordance with ]. ''

	It may be useful to put some of it under the first heading ("Reactive centrifugal force"). ] (]) 13:37, 5 March 2008 (UTC)

	In addition, I now see that also the definition was changed without discussion, and it looks less good to me than the one that we had settled on. Thus I revert, moving the alternative version here:

	''* A '''real''' or "''']'''" centrifugal force occurs in reaction to the ] of a mass. If a freely rotating body remains intact (i.e., does not distort or break apart), the centrifugal force measured at any point in or on that body exactly equals the ] directed toward the axis of rotation at that same point.''

	IMHO, that definition corresponds less to the way Newton presented it and obscures the fact that force is due to acceleration; it lacks the clarification that it is the force that originates from the passive body. ] (]) 21:47, 5 March 2008 (UTC)

	== The centrifuge ==

	Does the centrifugal force that causes stuff to move to the outer edge of a centrifuge come under the real or fictitious category? If it is real, it is certainly not a reactive force. If it is fictitious, it has got a very real effect.

	I suggest that the introduction be tidied up such as to define centrifugal force without splitting it into a real kind and a fictitious kind. ] (]) 11:01, 4 April 2008 (UTC)

	: There happen to be two competing (and incompatible) uses of the term, and lack of perception of the differences continues to cause many confusions and even disputes in academia. Thus, how do you propose to do such "cleaning up" without recreating the kind of confusion that this article gets rid of from the start?
	: About your example: There is no real direct force that causes stuff to move to the outer edge; such a hypothetical force can have no real effect. However, moving objects resist changing their trajectory, and that causes a very real reactive force against the centrifuge wall. Do you think that it may be useful to add this example? ] (]) 16:19, 6 April 2008 (UTC)

	Harald88, In planetary orbital theory, an elliptical orbit is the result of an inward radial force of gravity and a very real outward radial force which is the centrifugal force.

	In the centrifuge, gravity is neglible and so we only have the centrifugal force.

	The orbital solution to a centrifugal force acting in isolation without gravity is an infinitely eccentric hyperbola. This translates into a straight line in the laboratory.

	In the centrifuge, a very real effect occurs, but you say that this is simply due to the tendency of moving objects to resist changing their trajectory. This tendency is known as inertia and it is equivalent to centrifugal force in the laboratory. It is a very real effect.

	Hence, I do not accept that centrifugal force is a fictitious effect. If it can bring about a real effect in a centrifuge, then it is real. ] (]) 07:29, 16 April 2008 (UTC)

	: You did not answer my question. Do you think that it may be useful to add this example? ] (]) 09:21, 20 April 2008 (UTC)

	Harald88, By all means put in a section about the centrifuge. It totally undermines the existing introduction which tries to claim that centrifugal force applies to two different things, one real and one fictitious, which just happen to act in the same place at the same time.

	In the centrifuge, would they try to argue that the centrifugal force only becomes real at the moment when the heavy particles hit the edge?

	That would be the same as saying that gravity for a man falling over a cliff only becomes real when he hits the ground. ] (]) 13:28, 21 April 2008 (UTC)

	== Is it real or fictitious? ==

	The main article seems to be hedging its bets. It claims that there are two kinds of centrifugal force, with one kind being real and the other kind being fictitious. It then gives examples of each kind but goes on to admit that both of these kinds are the same thing.

	The problem seems to be that modern literature presents centrifugal force to be a fictitious force, whereas classical literature presents it as a real force.

	Even in the absence of a resolution of this controversy, the main article needs to be tidied up. We need to explain what centrifugal force is, without mentioning whether it is real or fictitious.

	There then needs to be sections giving reasons for suggesting that it is fictitious, and sections giving reasons for suggesting that it is real.

	But in its current form, the article is unsatisfactory because it talks of two kinds of centrifugal force when in fact there is only one kind. ] (]) 05:45, 18 April 2008 (UTC)

	: No, the two uses are entirely incompatible, and I thought that the article makes that clear - one of the purposes of this article is to end such confusion and misjudgment. Where did you get that idea, which sentence needs to be improved?
	: Note also that the article refers to a modern encyclopdia (edition of 2007) that defines centrifugal force as a reaction force.
	: Thanks, ] (]) 09:19, 20 April 2008 (UTC)

	::Harald88, the example of the swerving car in the so-called consensus version totally undermines what you have just said. It is trying to make out that the fictitious centrifugal force and the real centrifugal force are the same thing depending on how you view it.

	::The version which I put in, which you didn't see because it was changed by Thermochap, merely states the facts as regards what centrifugal force is. It then points out that it used to be regarded as real, but that it is now regarded as fictitious. If you say that a 2007 encyclopaedia states that it is real, then that is a clear sign that there is no consensus on the matter within the physics community. ] (]) 12:31, 20 April 2008 (UTC)

	== The Introduction ==

	Thermochap, I thought that the middle paragraph of your new introduction was unnecessarily complicated. It involved the Affine connection. Overall, I'm not happy with it because you have acknowledged that centrifugal force is a real reaction to a centripetal force and then brushed that fact under the carpet as being history. What do you call that real reaction effect now if it is no longer considered to be centrifugal force?

	Meanwhile, you have emphasized the modern view that centrifugal force is only a fictitious effect as viewed from a rotating frame of reference, when in fact you are perfectly aware yourself that the effect is real.

	I had deliberately worded the article in such as way as to point out that nowadays, centrifugal force is considered to be fictitious, whereas in days of old, it was considered to be real.] (]) 08:14, 20 April 2008 (UTC)

	: David, we have been through all this ]. It is clear to everybody that you don't understand the first thing about this article's subject. Please do not try to edit it, your attempts to do so invariably make the article wrong and completely out of tune with established physical understanding. I have reverted it. –] 08:19, 20 April 2008 (UTC)

	:: Indeed, the use of the term as reaction force is less common nowadays, but that "old" meaning is related to Newtonian mechanics which led to the derivation of centripetal acceleration; which in turn is necessary for understanding the fictitious use of the term. Thus, although at a time I went along with putting the fictitious meaning first because of its greater popularity, for a logical and comprehensible explanation to the reader it is certainly better as it is now.
	:: In spite of that, as long as people like David turn up, it appears that it is still not well enough explained - or perhaps the topic is just to difficult? I'm not sure. David, what should be changed so that you won't find it confusing anymore?
	:: Thanks, ] (]) 09:14, 20 April 2008 (UTC)

	::: I actually think that the introduction is better off without any reference to the archaic use of the term "centrifucal force" to denote the reaction force to a centripetal force. That could still be in the article, but somewhere nearer the end. I also think that it needs to be made clear early in the article that the term "fictitious force" has a very specific meaning. It is not the same as "fictional". It is not the opposite of "real". It is a force that enters the calculations when a non-inertial reference frame is used. --] (]) 17:28, 20 April 2008 (UTC)

	:::: I agree with these points, mostly. However, we should be careful not to move the reaction force so far down that it appears to be merely a historical curiosity that can safely be skipped. That's what it is, of course, to one who groks the fictitious force, but it seems to me that regrettably often people confuse the two forces. Therefore readers deserves to have the difference between them explained in some detail. And it is far nicer to do that by saying, "here is an older meaning of the word, but beware that it is different from the mainstream meaning in such-and-such way", than to have to say "here is a stupid misconception that you must disabuse yourself of". Of course we can only do this because we have sources to show that the achaic sense of the term is not complete fuction -- but given that we do have those, grabbing the chance sounds like a good idea. –] 22:25, 20 April 2008 (UTC)

	::::: Actually, because the reaction force is precisely a historical curiosity that can safely be skipped, I think it does more harm than good to give it a prominent position. Lots of people just read the first paragraph, and they should get as good info as possible. We should keep the text as clear as possible, and keep distractions to a minimum. --] (]) 20:49, 21 April 2008 (UTC)

	== The Consensus Version ==

	Henning, In the so-called consensus version, you talk about two kinds of centrifugal force. You talk about a real kind, and then you talk about a fictitious kind.

	Below that, you then describe a scenario in which centrifugal force is either real or fictitious according to how you look at it.

	This is entirely unsatisfactory.

	The version which you reverted was not mine. In the version which I put in yesterday, I merely described centrifugal force and then pointed out the fact that it used to be considered to be real, but that nowadays it is considered to be fictitious.] (]) 12:35, 20 April 2008 (UTC)

	:: No. The consensus version describes that the term "centrifugal force" has two different possible meanings, and then goes on to describe a situation that happen to illustrate both meanings. But even in the described situation the two meanings of "centrifugal force" refers to two ''different'' forces. –] 22:11, 20 April 2008 (UTC)

	: David, The centrifugal force was ''never'' considered to be real by Newton, Maxwell, or Bernoulli. If you want to put a statement like that you need to cite a source. Specifically you need to cite a source that says "the centrifugal force was considered to be real", or something very similar to that. If you read a text by, say Maxwell, and interpret that as him saying that the centrifugal force is real, that is still original research, since it is your interpretation of what he says. --] (]) 17:16, 20 April 2008 (UTC)

	Thermochap pointed out this nice animation from commons:
	]
	which nicely shows the difference between the two meanings described in the article. The red arrow is the centripetal force; the magenta one is the reactive centrifugal force, and the blue one is the fictitious force. I think this would make a good illustration for this article, if only the blue arrow had been decomposed into centrifugal and Coriolis terms after the green ball is let go.
	Names, aside, the force shown in magenta is and always was considered to be real; that shown in blue is and always was considered to be fictitious. –] 22:45, 20 April 2008 (UTC)

	::Henning, centrifugal force has only one meaning. The controversy lies in whether or not it is real or fictitious. The official position today is that it is fictitious. However, in former times, it was considered to be real.

	::I don't quite follow PeR's logic that if I were to provide a quote from an old paper confirming that centrifugal force was believed to be real, that this would have to be dismissed on the grounds that it was my original research.

	::The present introduction is totally unsatisfactory because it is trying to fudge the controversy by stating that the term centrifugal force has two different possible meanings.

	::The new introduction which I put in yesterday simply stated what centrifugal force is, and then further stated that the modern consensus is that centrifugal force is fictitious, whereas previously it had been regarded as real.] (]) 07:11, 21 April 2008 (UTC)

	::: If you don't understand what I said, then read ]. Then read what I said again. I'm tired of repeating myself. --] (]) 07:57, 21 April 2008 (UTC)

	== Admissibility of Evidence ==

	PeR, I think that you are going to have to repeat yourself. We need to get something straight here regarding the issue of admissibility of evidence. You declared that centrifugal force was never considered to be real. You further went on to state that if I were to produce any quotes from Newton or Bernoulli which indicated that they believed that centrifugal force was real, that this would not be deemed to be admissible evidence on the grounds that it would be my own original research.

	Here is a quote from Bernoulli out of the ET Whittaker book on the history of aethers.

	''"The elasticity which the Aether appears to possess, and in virtue of which it is able to transmit vibrations, is really due to the presence of these whirlpools; for, owing to centrifugal force, each whirlpool is continually striving to dilate, and so presses against the neighbouring whirlpools."''

	And here is a quote from Maxwell's paper 'On Physical Lines of Force',

	''"The explanation which most readily occurs to the mind is that the excess of pressure in the equatorial direction arises from the centrifugal force of vortices or eddies in the medium having their axes in directions parallel to the lines of force"''

	And you are trying to tell me that this is not evidence to suggest that Bernoulli and Maxwell believed that centrifugal force was real?

	: '''YES!''' I am trying to tell you that this is not evidence to suggest that Bernoulli and Maxwell believed that centrifugal force was real. However, if you don't want to accept this you don't have to. Just don't write anything in the article. If you do want to write something like that then you must (and here I am repeating myself, as requested) ''cite a source that says "the centrifugal force was considered to be real" or something very similar to that. If you read a text by, say Maxwell, and interpret that as him saying that the centrifugal force is real, that is still original research, since it is your interpretation of what he says.'' --] (]) 19:42, 21 April 2008 (UTC)

	PeR, There is a controversy about whether or not centrifugal force is real. The official position today is that it is not real.

	The current introduction is abominable because it tries to fudge the issue by pretending that there are two centrifugal forces. One for the realists, and one for the fictitiousists. This is an extreme case of ecclecticism. The current introduction cannot remain because it is a total disgrace.] (]) 08:02, 21 April 2008 (UTC)

	: You misinterpret what it says. However, the fact that you don't understand it is evidence that it is not clearly enough written, so I agree that it should be rewritten. --] (]) 19:42, 21 April 2008 (UTC)

	== Suggestions for improved and simplified introduction ==

	PeR, I'm glad that you agree that the introduction should be re-written. So let's take it one step at a time.

	First of all, I assume that we are both agreed that somewhere in the introduction there should be a statement clarifying that we should not be confusing centrifugal force with centripetal force.

	And now, how about this for an introductory sentence?

	''"When an object is constrained to move in circular motion, an outward radial force will be observed to act on that object"''

	Would you agree that that is a correct statement of fact? There is certainly no need to distinguish between the reactive kind and the other kind because they are exactly the same effect.

	Beyond that, I can't think that much more is needed in the introduction other than to state that a controversy exists regarding whether or not it is real or fictitious. ] (]) 02:13, 22 April 2008 (UTC)

	:: Your proposal is not a correct statement of fact. It is simply false. An outward centrifugal force appears to act on an object only when it is described in a rotating coordinate system - and then not just for objects moving in circles, but for ''all'' object that are observed in that coordinate system. The outwards force that appears in an inertial system when an object moves in a circle ''does not act on the object that moves circularly'', but on the constraints that make it move in a circle. This is clearly described in the article (at least when you have not recently vandalised it), and there are several descriptions of it to be found on this talk page.
	:: Your continued assertions that these two forces are the same force are simply wrong. The two forces do not even apply to the same body. There is no controversy whatsoever about whether any of these forces are real or fictitious. Everybody agrees that the reactive force is (usually) real; and everybody agrees that the fictitious force is fictitious. Nothing of this will change because you continue to claim that it is false. –] 04:11, 22 April 2008 (UTC)

	Henning, you are making it more complicated that it is. When an object is constrained to move in a circle, then an outward centrifugal force will act on it.

	And there is a controversy about whether centrifugal force is real or fictitious. And there is only one centrifugal force. It is sheer double talk to split centrifugal force into two in order to cater for both beliefs. ] (]) 04:44, 22 April 2008 (UTC)

	:: David, read what Henning wrote again. Your proposal is not a correct statement of fact. It is simply false. --] (]) 07:04, 22 April 2008 (UTC)

	PeR, OK, let's go through Henning Makholm's reply stage by stage. He says,

	''An outward centrifugal force appears to act on an object only when it is described in a rotating coordinate system''

	The very fact that we state the word 'outward' describes the effect perfectly without having to mention anything about rotating coordinate systems. Henning Makholm is making it more complicated than it is.

	He then states,

	''- and then not just for objects moving in circles, but for ''all'' object that are observed in that coordinate system.''

	This statement was totally unnecessary because all objects that are observed in that coordinate system will be partaking in the circular motion in question. This was just a clouding statement.

	He then states,

	''The outwards force that appears in an inertial system when an object moves in a circle ''does not act on the object that moves circularly'', but on the constraints that make it move in a circle.''

	What happens in a centrifuge regarding the large particles before they reach the edge? Is the centrifugal force not acting on them?

	He then says,

	''Your continued assertions that these two forces are the same force are simply wrong. The two forces do not even apply to the same body.''

	It's only in Henning Makholm's imagination that there are two centrifugal forces. No textbook ever states such a notion.

	As for Henning Makholm's claim that the two forces don't even apply to the same body, he is only making the matter worse. In the example in the introduction to the main article, the bit that you call the fictitious centrifugal force acts to throw the man towards the car door. The bit which you call the reactive centrifugal force occurs by virtue of the man pushing against the car door as a result of that very same centrifugal force.

	And he is saying that these two centrifugal forces do not act on the same body. It's like saying that the force with which a man hits the ground is not the same force as the gravity which caused him to fall over the cliff.

	The man pushes against the car door because of the one and only centrifugal force.

	I need to have a citation which specifically states that centrifugal force applies to two different forces. ] (]) 08:04, 22 April 2008 (UTC)

	: I agree with your last statement. We need to cite a science-history book that states that Newton and others used the word "centrifugal force" with a different meaning than that which is used today. (The current references only show the usage of the term, which is not the same thing.) The rest of your analysis is just plain wrong. Sorry. My best advice is that you try reading the ] article, some elementary mechanics textbooks, and then try reading Hennings text again. --] (]) 10:00, 22 April 2008 (UTC)

	PeR, so far your entire contribution to this debate has been to state that I am wrong and that I should read more of what Henning Makholm has to say, as if by reading his nonsense over and over again, then I might actually believe it eventually.

	I'd like to hear your own analysis of the situation.

	Let's go back to the very beginning. Tell me at what point this basic sentence goes wrong,

	''The centrifugal force is an outward radial force that acts on any object that is constrained to move in circular motion''.] (]) 13:32, 22 April 2008 (UTC)

	: Your statement doesn't properly describe the fictitious force (modern use of the term "centrifugal force"), because it fails to mention the rotating reference frame. It doesn't describe the reaction force (Newton's use of the term), because it says that it acts on the object itself, not the thing which is constraining it to move in a circle. --] (]) 13:53, 22 April 2008 (UTC)

	PeR, the fact that the object is constrained to move in circular motion caters for the rotating frame of reference aspect. As for the reaction bit, that can be dealt with in the main body of the article. That is an extension of the concept. A body which is being acted upon by a centrifugal force naturally transmits this force on when it comes into contact with another body. <small>—Preceding ] comment added by ] (] • ]) 14:38, 22 April 2008 (UTC)</small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

	== The reasons for the reversion of the wikified version ==

	The wikified version is teaching the false doctrine that centrifugal force is a term which applies to two different forces.

	This doctrine is based on the idea that the centrifugal force which throws the passenger towards the door of the swerving car is a different force from the force which the passenger eventually causes on the door when contact is made.

	The argument goes that a fictitious force throws the passenger to the car door and when contact is made, this is then transmitted into a real force which pushes against the door.

	Such an argument is the same as saying that the force which an object causes on the Earth's surface due to its weight is a different force from the gravitional force that pushes the person against the surface of the Earth.

	There is one force of gravity, and there is one centrifugal force.

	The introduction to the article must describe in as simple terms as possible what that one centrifugal force is.] (]) 13:47, 22 April 2008 (UTC)

	:I don't know whether what you say is true or not, but please IF you are going to rewrite the article, rewrite it in such a way that the article is wikified! ] ] 15:01, 22 April 2008 (UTC)

	:Looking at both versions of the text, I have to say it looks as though reverting was correct, but I'm no physicist. Have you guys thought of trying ] and getting another opinion? ] ] 15:29, 22 April 2008 (UTC)

	In the old days, before about 1950, physics books called centrifugal force an inertial force. In those days inertial force was the term used for what today are labeled fictious forces. What this means is that the force is frame dependent. The force can be made to go away by simply switching from a noninertial frame to an inertial frame and the force disapears. The older terminology is certainly less of a problem, since students now wonder what is this fictious force? in my view the entire discussion of this is confusing and of questionable value as part of the article. There are no fictious forces, since they dont exist by definition of the word. So saying centrifugal force is fictious is the same as saying it doesnt exist. But since it does exist, that is bound to create confusion. I propose using the term frame dependent force since that captures the essential meaning of what is happening and we get rid of this textbook stupidity of fictious forces.] (]) 16:07, 22 April 2008 (UTC)

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Not to be confused with

There are various warnings not to confuse various forces: Centrifugal force, Reactive centrifugal force, Centripetal force, Centrifugal force (rotating reference frame). There is however no discussion of the distinction between these various phenomenon. --Kvng (talk) 20:46, 2 July 2012 (UTC)

More properly an effect than a force?

I suspect that the lead would be better if reworked à la N.M.J. Woodhouse, who writes (p. 7) in his Special Relativity (Springer-Verlag, 2003),

"In problems where the rotation matters, for example in the analysis of Foucault's pendulum, it is helpful to treat a terrestrial frame as if it were intertial, but to introduce correction terms, the 'fictitious' centrifugal and Coriolis forces, to take account of the rotation. But these are not real forces, and the frame is not really inertial."

Indeed, even Misplaced Pages's own article on Coriolis forces is a redirect to Coriolus effect, and that article makes it clearer than this one does that the force is only apparent. I'd have just changed it myself, but wondered if there were a good argument for retaining the nonparallelism of treating one of the two forces as though it were somehow less fictitious than the other.—PaulTanenbaum (talk) 20:57, 19 February 2013 (UTC)

My two cents here - I think there is a distinction between "effect" and "force" in these instances. My feeling from the literature that I've read is that the effect refers to the apparently anomalous deflection of the path of a particle while the force is the pseudo-force or fictitious force that is introduced to explain the deflection. As for an argument for retaining the nonparallelism, this is what we find in the literature, ie the terms "Coriolis effect" and "Coriolis force" are used with about the same frequency and sometimes it seems inter-changeably. The choice also seems to be dependent on the context - in meteorology we find "Coriolis effect" (and my guess this is true for the everyday person), while in the physics literature "Coriolis force" is more common. I don't think the same can be said for "centrifugal force"/"centrifugal effect". Just to get a general idea of how common the terms occur in the literature I searched for each phrase in google books:

Coriolis effect : ~44,500
Coriolis force : ~138,000
Centrifugal effect : ~16,700
Centrifugal force : ~1,260,000

That's almost two orders of magnitude difference for centrifugal between effect and force, while for Coriolis the two are roughly equal (okay, a factor of about 3 but less than an order of magnitude). So imo I don't care whether the other article is "Coriolis effect" or "Coriolis force", but I strongly favor keeping this one as "centrifugal force" per the usage frequency in the literature. That being said, if the intro needs to be clearer on it being a fictitious force then that should be fixed. --FyzixFighter (talk) 05:33, 20 February 2013 (UTC)

I agree with FF. If you want it more parallel, go the other way. And I'd avoid the notion of "only apparent", since we already have a well-define notion of "fictitious force" that says exactly what it is. Dicklyon (talk) 05:49, 20 February 2013 (UTC)

Acceleration Derivation

In the derivation section, I'm noticing that the last two lines of equations in the "acceleration" section do not seem to follow from one another. When I evaluate the d/dt(+w x r) term in the next to last line, it does not give the factor of two in front of the Coriolis term. I believe the error is leaving out part of the first derivative operator: that is, in that equation, instead of the operator "d/dt" we should have "d/dt + w x" as the operator. (also see the rotational reference frame wiki page for that derivation, in which the derivation correctly gets the factor of two into the Coriolis term) I would just go ahead and add it, except I'm not at all familiar with the proper coding for inserting equations into wikipedia, and am very new here in general — Preceding unsigned comment added by 222.221.253.76 (talk) 02:13, 6 March 2013 (UTC)

It is correct. Don't forget that

{\frac {\operatorname {d} {\boldsymbol {r}}}{\operatorname {d} t}}=\left+{\boldsymbol {\omega }}\times {\boldsymbol {r}}\ ,

and of course likewise

{\frac {\operatorname {d} }{\operatorname {d} t}}\left=\left+{\boldsymbol {\omega }}\times \left\ ,

so that is where the second term comes from.

Note - this derivation could need a source. - DVdm (talk) 12:47, 6 March 2013 (UTC)

It's the rotation of the direction of the velocity vector that matters, not of the frame.

Yep. We have here a misleading article title, and misleading wording that implies that a reference frame's rotation results in centrifugal force/pseudoforce. Rather, it's the centripetal acceleration of the frame (or object) that results in such forces. The centripetal acceleration of the frame (stated in an inertial frame) is proportional to the rate of change of the direction of the velocity vector (also stated in the same inertial frame). Thus, if the rate of rotation of anything matters, it's the rate of rotation of the direction of the velocity vector, not the rotation rate of the frame.

I grant that, in most usual cases (such as ball-on-string), the most common frame is attached to the object (ball) and is also rotating along with the object. The rotation rate of the frame in these cases is the same as the rotation rate of the direction of the velocity vector, but that's only incidental. It's the rate of change of the direction of the velocity vector that makes for the centrifugal forces here. If the frame was still attached to the ball, but was chosen to rotate at twice or three times the rate of the velocity vector, or if it was chosen to not rotate at all, it would not effect the magnitude of the centrifugal force, nor would it effect the actual direction of the centrifugal force. Such an independently-rotating frame would have different numbers representing the direction of the centrifugal force, but the actual direction (or magnitude) of the centrifugal force at any particular moment would not vary with rotation rate of the frame.

We should not muddle-together the movement of a frame (such as in a circle about a point) with rotation of the frame. They are two different things that can be independent. If we don't keep that in mind, it leads to fallacies.

Montyv (talk) 17:32, 31 May 2015 (UTC)

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