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Re: physics of bouncing



On Tue, 13 Mar 2001, John S. Denker wrote:

I assert:
B1) The decay with the anvil is only slightly faster than the decay without
the anvil.

B2) Air resistance remains the dominant dissipative mechanism.

B3) Internal friction within the ball is the second most important
dissipative mechanism. This friction applies to internal modes excited by
the collision process.

I don't disagree with the thrust of JD's comments, however, I
think they are somewhat undermined by these "assertions."

Given B2 and B3, B1 would certainly follow, but I'd have to say
that my gut reaction is to be highly skeptical. Extrapolating from
my own experience, I would expect the superball to swing freely
far longer than it would bounce against *any* surface. And, of
course, this would be precisely because internal friction
dominates.

I *can* imagine that the superball anvil *system* would retain its
motion (if observed carefully) for a longer time since the
sequence of collisions will give the anvil some small amount of
energy and its enormous inertia makes *it* vastly less susceptible
to the effect of air resistance.

John Mallinckrodt mailto:ajm@csupomona.edu
Cal Poly Pomona http://www.csupomona.edu/~ajm