
#37
Jan2913, 09:51 AM

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Having tried those ideas on teenagers, not long ago, I did find it worked with some. It didn't work with others but, so what? They'll have ended up in banking or as 'TV personalities'. 



#38
Jan2913, 09:53 AM

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#40
Jan2913, 10:48 AM

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#41
Jan2913, 10:57 AM

P: 1,657

There is nothing confusing about these rules, and there are no exceptions for "fictitious forces" or "noninertial frames". The only complicated thing is that you need to realize that a vector can change for two reasons: (1) the components change, or (2) the basis vectors change. It might be simpler to pretend that (2) never happens, but it's a falsehood, and you're doing physics in a crippled way when you do it. 



#42
Jan2913, 11:08 AM

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#43
Jan2913, 11:33 AM

P: 343

It appears because of choice of coordinates and reference frame, and yes it does not exist in inertial reference frame.




#44
Jan2913, 12:33 PM

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P: 6,572

Example: there is no centrifugal reaction force to the weight of a car sitting on a road on the equator, even though the car is whipping around at 1000 mph. as the earth turns and even though it's weight bears on the earth surface. Ques. What about the normal force? Do we call that a centrifugal force? Answer: no. Ques. But it is directed away from the centre of rotation (ie. up). Answer: Yes, but we do not call it centrifugal. Ques. Why not? Answer: My answer would be: We don't call it centrifugal because it does not cause anything to flee the centre of rotation. I am not sure what your answer would be. Should we call it centrifugal? AM 



#45
Jan2913, 01:09 PM

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P: 6,925

Change this 2 body system to one where there are no attractive forces, and the two objects are connected by a string and rotate in a circular path about a common center of mass. Both objects exert a reactive centrifugal force on the ends of the string (assuming that the common center of mass is not located within one of the objects, in which case only one end of the string experiences a reactive centrifugal force). 



#46
Jan2913, 05:46 PM

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AM 



#47
Jan2913, 05:55 PM

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P: 6,572

AM 



#48
Jan3013, 03:44 AM

P: 3,543





#49
Jan3013, 03:48 AM

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In classical mechanics we treat the Coriolis force, the translation inertial force and the centrifugal force on equal footing.
I wonder why only the centrifugal force is poorly understood by people, since it's the only inertial force generating multipage debates o PF... 



#50
Jan3013, 06:09 AM

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#51
Jan3013, 06:34 AM

P: 1,657

Surely, the last step isn't doing anything for you. Calling them "forces" doesn't help anything. They are different from other forces you're likely to encounter, because they don't depend on the substance an object is made of, and they don't have an equal and opposite reactive force. Calling them forces is a confusionit's not a simplification. There is nothing that becomes simpler because of that choice of names. The real confusion that is at the heart of discussions of "inertial forces" is the assumption that, if [itex]\stackrel{\rightarrow}{U}[/itex] is a vector (say, a velocity vector) with components [itex]U^i[/itex], then [itex]\frac{\stackrel{\rightarrow}{dU}}{dt}[/itex] must be a vector with components [itex]\frac{dU^i}{dt}[/itex]. That's just bad mathematics. It's just not true. It's true for inertial Cartesian coordinates, but not for other coordinates. It's not a "simplification" to assume something that is provably false. 



#52
Jan3013, 07:39 AM

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#53
Jan3013, 08:34 AM

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