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Wellll.... as a matter of fact, you can't directly feel coriolis or centrifugal force.But I'd also like to point out that you can't directly feel gravity either; if you fall off a roof, you can not feel anything, yo cannot feel gravity, but the deceleration hurts a lot at the bottom. So you indirectly feel gravity that way. Likewise you can feel centrifugal or coriolis force when something prevents it from acting.

Well, in that case, magnetism doesn't really exist either; it's just moving charged particles and relativity.(At least it is unless or until somebody finds a magnetic monopole, if that ever actually happens, in the meantime all known magnetic fields are just electric fields.)

Wellll.... as a matter of fact, you can't directly feel coriolis or centrifugal force.

This is also wrong.Likewise you can feel centrifugal or coriolis force when something prevents it from acting.

It's often convenient to choose a rotating reference frame in which the subject doesn't rotate; that's the main point.

Quote from: wolfekeeper on 02/05/2012 23:39:13I'm pretty sure a significant number of TNS subscribers are now convinced that, because they can "feel" a centrifugal force, it's a real force. I think that's unfortunate.What I think is unfortunate is that people think that inertial forces are not real forces and that real forces are different from non-inertial force in some significant way.

I'm pretty sure a significant number of TNS subscribers are now convinced that, because they can "feel" a centrifugal force, it's a real force. I think that's unfortunate.

Your page proves exactly why...

you can't group inertial forces together with "real" forces (or whatever other term you want to use for them.)

They're caused by different things and behave differently under transformations of reference frames (in particular, inertial forces vanish in inertial reference frames). Grouping them all together is misleading.

Centrifugal force (and coriolis force) are pseudo forces due to a combination of rotation of the reference frame and momentum; and they are needed when you are analysing a situation in a rotating reference frame to get the correct movements; together they explain why the stars spin around the Earth (for example).

Quote from: wolfekeeper on 02/05/2012 21:55:53Wellll.... as a matter of fact, you can't directly feel coriolis or centrifugal force.But I'd also like to point out that you can't directly feel gravity either; coriolis forces and centrifugal forces are considered gravitational forces in general relativty.

Wellll.... as a matter of fact, you can't directly feel coriolis or centrifugal force.But I'd also like to point out that you can't directly feel gravity either;

That is not true. One can't say "This kind of force transforms in this way while this other force transforms in this other way." How something transforms is determined only by the theory being used.

To be clearer, inertial forces are proportional to mass, ...

Quote from: JP on 03/05/2012 19:43:25To be clearer, inertial forces are proportional to mass, ...I thought I had stated that already. Sorry if I missed that.

By the way, what model are we assuming for this debate? The mantra centrifugal force is not a force is usually used when teaching Newtonian mechanics in inertial reference frames.

A tourist in a powered interplanetary rocket feels "gravity." Can a physicist by local effects convince him that this "gravity" is bogus? Never, says Einstein's principle of the local equivalence of gravity and accelerations. But then the physicist will make no errors if he deludes himself treating true gravity as a local illusion caused by acceleration. Under this delusion, he barges ahead and solves gravitational problems by using special relativity: if he is clever enough to divide every problem into a network of local questions, each solvable under such a delusion, then he can work out all influences of any gravitational field. Only three basic principles are invoked: special-relativity physics, the equivalence principle, and the local nature of physics. They are simple and clear. To apply them, however, imposes a double task: (1) take spacetime apart into locally flat pieces (where the principles are valid), and (2) put the pieces together into a comprehensible picture. To undertake this dissection and reconstruction, to see curved dynamic spacetime inescapably take form, and to see the consequences for physics: that is general relativity.

Notice that all inertial forces have the mass as a constant of proportionality in them. The status of inertial forces is again a controversial one. One school of thought describes them as apparent or fictitious which arise in non-inertial frames of reference (and which can be eliminated mathematically by putting the terms back on the right hand side). We shall adopt the attitude that if you judge them by their effects then they are very real forces.

Can gravitation and inertia be identical? This question leads directly to the General Theory of Relativity. Is it not possible for me to regard the earth as free from rotation, if I conceive of the centrifugal force, which acts on all bodies at rest relatively to the earth, as being a "real" gravitational field of gravitation, or part of such a field? If this idea can be carried out, then we shall have proved in very truth the identity of gravitation and inertia. For the same property which is regarded as inertia from the point of view of a system not taking part of the rotation can be interpreted as gravitation when considered with respect to a system that shares this rotation. According to Newton, this interpretation is impossible, because in Newton's theory there is no "real" field of the "Coriolis-field" type. But perhaps Newton's law of field could be replaced by another that fits in with the field which holds with respect to a "rotating" system of co-ordinates? My conviction of the identity of inertial and gravitational mass aroused within me the feeling of absolute confidence in the correctness of this interpretation.

From the standpoint of an observer in the accelerating frame, the inertial force is actually present. If one took steps to keep an object "at rest" in S', by tying it down with springs, these springs would be observed to elongate or contract in such a way as to provide a counteracting force to balance the inertial force. To describe such force as "fictitious" is therefore somewhat misleading. One would like to have some convenient label that distinguishes inertial forces from forces that arise from true physical interactions, and the term "psuedo-force" is often used. Even this, however, does not do justice to such forces experienced by someone who is actually in the accelerating frame of reference. Probably the original, strictly technical name, "inertial force," which is free of any questionable overtones, remains the best description.

Whenever the motion of the reference system generates a force which has to be added to the relative force of inertia I’, measured in that system, we call that force an “apparent force.” The name is well chosen, inasmuch as that force does not exist in the absolute system. The name is misleading, however, if it is interpreted as a force which is not as “real” as any given physical force. In the moving reference system the apparent force is a perfectly real force, which is not distinguishable in its nature from any other impressed force. Let us suppose that the observer is not aware of the fact that his reference system is in accelerated motion. Then purely mechanical observations cannot reveal to him that fact.

Quote from: JP on 03/05/2012 20:03:15By the way, what model are we assuming for this debate? The mantra centrifugal force is not a force is usually used when teaching Newtonian mechanics in inertial reference frames. I don't know where you got that idea. Typically it's undergrad courses which some teach that, i.e. Physics I, II, III. Not in more advanced courses. SeeMore modern teachings give the following...sorry, you cannot view external links. To see them, please REGISTER or LOGINMost notably, From Gravitation, by Misner, Thorne and Wheeler, Box 6.1, page 164 . . .

My point still holds that when we Newtonian mechanics in inertial reference frames (usually in the first course of an undergraduate physics education), centrifugal force is not a force in that model. It doesn't matter what models they'll learn later--it doesn't make centrifugal a force magically a force in inertial Newtonian mechanics simply because general relativity exists.

The correct spelling for the short term of mathematics is "math" and not "maths". In any case I never seen a mathematician of physicist use the term "maths" In the last 30 years.

So... we all know forces (except gravity) are mediated by fields which are made up of virtual particles. We have photons for electromagnetism, gluons for the strong force, W and Z bosons for the weak force...So are there any centrifugons?

My point still holds that when we Newtonian mechanics in inertial reference frames ... centrifugal force is not a force in that model.

Well that's part of my point that this entire argument hinges on which model you choose to use.

Anyway, regarding the fundamental particles, I wasn't trying to prove or disprove anything. I'm legitimately curious. I suspect there might actually be "centrifugons." After all, we suspect that gravity is governed by gravitons, and "centrifugal force" is an inertial force like gravity. Would inertial forces also be governed by gravitons? I don't know, but its interesting.

I find the following comments confusing:Quote from: JP on 03/05/2012 20:41:48My point still holds that when we Newtonian mechanics in inertial reference frames ... centrifugal force is not a force in that model.What you've said here, literally, is "In inertial frames of reference, inertial forces don't exist and when they don't exist they are not forces?"See my confusion? Sorry I didn't cacth myself earlier.

Class 1) The Newtonian viewpoint: gravitation is merely an artifact of looking at things from the 'wrong' point of view. (See Peacock in link above)

Class 2) From the standpoint of an observer in the accelerating frame, the inertial force is actually present. If one took steps to keep an object "at rest" in S', by tying it down with springs, these springs would be observed to elongate or contract in such a way as to provide a counteracting force to balance the inertial force. To describe such force as "fictitious" is therefore somewhat misleading. (See A.P. French)

Ah yes, but my example was careful to avoid gravity.

Quote from: Geezer on 05/05/2012 02:52:45Ah yes, but my example was careful to avoid gravity.I was talking to JP, wasn't I?Pete

Will I have to conclude that my superior logic prevails?

I'll make this one last comment before I go back to bed. If one uses Netonian physics but insist that inertial forces are not real then one must accept that the gavitational force is not real because in Newtonian dynamics the force is proportial to the mass of body.

Quote from: Pmb on 06/05/2012 08:24:37I'll make this one last comment before I go back to bed. If one uses Netonian physics but insist that inertial forces are not real then one must accept that the gavitational force is not real because in Newtonian dynamics the force is proportial to the mass of body.That's why I was trying to leave gravity out of it In the example I gave, the subject stepped on to the platform while it was stationary. The platform then started to rotate, and the subject followed a curved path.Here's a restatement of the question:How was it possible for the subject to follow a curved path without a component of the force acting on him pointing towards the axis of rotation?

How was it possible for the subject to follow a curved path without a component of the force acting on him pointing towards the axis of rotation?