Talk:Reactive centrifugal force/Archive 3

Archive 1

Archive 2

Archive 3

the curved path

Noting the recent changes in the introduction, it´s true that a curved path follws from a centripetal force. It´s also true that there will be no reactive centrifugal force without a centripetal force. However, the outward tendency on rotation due to the inertia presupposes the existence of a constraint which would cause a centripetal force and hence a curved path. Therefore, has the curved path not perhaps been introduced prematurely in the introduction? May I suggest that you maybe reverse the order of those two sentences and tweak accordingly? 89.140.133.201 (talk) 20:22, 8 September 2014 (UTC) As in perhaps, ´´´ When a constraint opposes the outward motion, a centripetal force will act inwards on the object causing it to follow a curved path.´´´89.140.133.201 (talk) 20:28, 8 September 2014 (UTC)

Except that the inertia isn't really strictly an outward tendency. It's a tendency to move in a straight line. If the source of the centripetal force is removed, the object doesn't just go radially outward but in a line tangent to the path it was following when the force is removed. For me, it's a more natural progression, similar to the ordering of the laws of motion, to say that the object is not following a straight line as inertia would have it do (1st law), therefore an external force is being applied (2nd law), therefore it is exerting a equal and opposite force on the source of the external force (3rd law). --FyzixFighter (talk) 01:45, 9 September 2014 (UTC)

I was examining the situation from the centrifugal clutch example. The inner shaft expands outwards under rotation. Curved paths and tangents don´t enter into it at this preliminary stage. Only the inertial effect is involved at this stage. The centriptal force comes into the picture only when the inner shaft makes contact with and is constrained by the outer shaft. Once centriptal force and reactive centrifugal force enter the picture, then we will have a curved (circular) path for each of the elements of the inner shaft, but the curved path is only incidental, whereas the causative mechanisms driving the device are rotation and the inertial effect. The tangent that ensues when the centripetal force is removed still involves an outward tendency, and the combined effect of the outward tendency of all elements around the rim of the inner shaft, is for the shaft to expand outwards. What you have written is technically correct, but people had been complaining about the top heavy wording. I could see that much of the top heavy wording centered around the involvement of the unnecessary term ´curved path´ so I attempted to illustrate the effect in question in more simple language using key terms such as inward, outward, center of rotation, constraint etc. As regards the clause about the directions being the same for both the reactive centrifugal force and the associated fictitious centrifugal force in the rotating frame, I was assuming as a matter of course that we were working around the same center of rotation, but I can see now that I should not have made that assumption for the reasons stated in the last paragraph of the inroduction. 141.105.106.140 (talk) 07:42, 9 September 2014 (UTC)

I'm all for simplicity, but not at the cost of being technically incorrect. The idea that inertia is a tendency to move in a straight line tangent to the curve is to me completely orthogonal to the idea that inertia is a tendency to move outward. I also think that it also doesn't work if we ever are dealing with non-circular rotation where the tangent line might correspond to decreasing radial distance. To only describe inertia in terms of the motion along the radius is to implicitly adopt a rotating, non-inertial frame (see EJ Aiton's, "The celestial mechanics of Leibniz in the light of Newtonian criticism" Annals of Science 18 (1):31-41 (2006)). Or, to quote Swetz, "Learn from the Masters!"

The question arises whether the earlier [Leibniz's] concept can be interpreted meaningfully. Considered as an endeavor of the circulating body, or a force acting on the body itself, it does not exist. But if we consider a reference frame fixed in the body and rotating with it, the body will appear to have an endeavor to recede from the centre. This is of course a fictitious force reflecting the acceleration for the reference frame.

I don't think I've ever seen a description of inertia, either in general or in the particular case of rotation), in a reliable source that says that it is an outward tendency of the object. Do you have one? It would certainly clear up this apparent disagreement. --FyzixFighter (talk) 03:04, 10 September 2014 (UTC)

It's true that nobody specifically defines inertia as an outward tendency, but inertia gives rise to straight line motion, which in the examples that we are looking at gives rise to an outward tendency. Put in 'straight line' if you want, it's fine. The important thing is that you don't put in 'curved path' before the constraining centripetal force has been introduced. It's looking OK now apart from the last paragraph in the lead. I think that Mook and Vargish have dreadfully confused the reactive force with the fictitious force. 94.173.45.184 (talk) 20:27, 10 September 2014 (UTC)

Indeed, the "outward tendency" that people speak of only makes sense in a rotating reference frame; let's not conflate those. I took out the "one could" sentence that you didn't like, since it seems to have no direct relation to actual practice or sources. Dicklyon (talk) 20:53, 10 September 2014 (UTC)

action-reaction pair

´´the fictitious force is felt by ALL objects in the rotation frame, unrelated to the action–reaction pair´´. True. But the clause that was removed about acting on opposite bodies was presumed only to apply to cases where the fictitious force IS involved in an action-reaction pair, but best to leave it out now because it was only an unnecessary extra in the introduction. 141.105.106.140 (talk) 08:20, 9 September 2014 (UTC)

What does it mean for a fictitious force to be involved in an action–reaction pair? I thought a fictitious force never had a reaction. If it had a reaction it would be a real force. Or do you have a counter-example in mind? Dicklyon (talk) 20:57, 10 September 2014 (UTC)

Interesting point. I had to think about it. I would say that in cases of actual rotation, the fictitious centrifugal force always forms an action-reaction pair with another fictitious centrifugal force, but that the existence of a fictitious centrifugal force does not mean that an action-reaction pair involving a reactive centrifugal force and a centripetal force also has to exist. But where such an action-reaction pair, as between a reactive centrifugal force and a centripetal force does exist due to the introduction of a constraint, then there will always also be a fictitious centrifugal force involved in the process, observable only in the rotating frame of reference, but whose effects can be felt in any frame of reference. 94.173.45.184 (talk) 12:31, 11 September 2014 (UTC)

No Original Research

I couldn't find any original research in the article. Reference 4 in particular lays out this very simple concept quite clearly. 81.4.183.162 (talk) 09:40, 12 October 2014 (UTC)

reactive centrifugal force

reactive centrifugal force applies to a push or a pull that is directed away from the center of rotation and it only occurs in situations where one body is in physical contact with another body, such as in the examples given in the main body of the article. The planetary example at the end of the lead involves only fictitious centrifugal force. There is no reactive centrifugal force involved in the planetary example. There is an action-reaction pair when considered over the two centripetal forces in the planetary example but these can never be considered to be centrifugally directed and they are not what this article is about. Centri-Fugal means center fleeing. Please don't insert this paragraph again without discussing further on the talk page. 81.4.183.162 (talk) 09:08, 14 October 2014 (UTC)

Looking at the Mook reference, I see that he is talking about a different use of the term 'reactive centrifugal force'. It therefore starts to get very confusing so it's best to deal with Mook's usage as in a section of its own. 81.4.183.162 (talk) 09:24, 14 October 2014 (UTC)

Roche Reference

The Roche reference has been used in this article to argue that the fictitious force is more commonly used than the reactive force. Page 403 in the Roche reference however according to my reading says the complete opposite http://www.marco-learningsystems.com/pages/roche/Motion_in_a_circle_pdf.pdf I'm looking at the part halfway down the first column where it reads,

"This is the centrifugal force of physics, an entirely fictional force [19]. It has now virtually disappeared from school and undergraduate physics textbooks because it can be highly confusing. Indeed, it is not uncommon even for physics authors to confuse the language of inertial and rotating frameworks."

I will remove that sentence in the lead as it appears to be ambiguous. If anybody wishes to restore it, I won't object. 94.173.45.184 (talk) 10:01, 15 November 2014 (UTC)

Inertia?

This article connects the fictitious or pseudoforce with inertia, and not the real action/reaction pair. Of course that's backwards, and wrong. It is the real action/reaction pair of forces that are caused by overcoming a body's inertia, by exerting a "real" force on it (one that follows Newton's third law). Also, this relation is exactly the same in the linear acceleration case. A pair of forces caused by overcoming a body's inertia certainly would not disappear in a rotating frame (or in the linear case, a linearly accelerated frame), so they are not an artifact of the accelerated or nonaccelerated observer. Inertia is not an artifact of the observer! Fictitious forces are noninertial.

Likewise, g-force and weight, wherever they occur, tend to smash things to strawberry jam, and it matters not who the observer is (jam happens). They all produce real action/reaction force pairs, are not fictitious, and not artifacts of frame-choice. So (again) this article has the relation backwards. Inertia is the thing that is connected to real forces, not fictitious forces. Overcoming inertia causes the strawberry jam. SBHarris 00:42, 31 July 2015 (UTC)