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Re: The old centrifugal force

On 11/15/2003 05:35 AM, Ludwik Kowalski wrote:
It is not hard to explain that a centripetal force, of some kind,
must exist to account for the centripetal (v^2/r) acceleration.

OK.

But it is hard to identify that force in some specific situations,

Why is it hard?

for example, when an object is sliding vertically inside a looping
track. If it is not an N3 reaction force then what is it?

To digress for a moment to another example, consider
a tetherball. The force is the tension in the string.
Is this not obvious?

Returning to the looping track: If you look closely
enough, there will be some sort of spring constant
associated with the track/wheel system. If the cart
tries to push itself "through" the track, the
spring forces will grow large enough to prevent that.
Call it a reaction force if you like. It's the same
"mechanical" force that keeps books from falling
straight through the tabletop.