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At 11:42 AM -0800 1/6/00, Leigh Palmer wrote:_______________________________________________
Something VERY strange is going on down here in the former colonies.
We just used a 2.8 meter long chain and saw and heard a SIGNIFICANT
time interval before the plastic ball arrived at the floor.
(isn't THIS result in keeping with the AJP video analysis?????)
I repeat:
JUST BECAUSE HEWITT SAYS IT, *DOESN'T* GUARANTEE THAT IT IS WRONG!!!!!!!
Thanks to Oren Quist I'm in the loop again. Oren faxed me the latest
"Figuring Physics" by the author of "Conceptual Physics", Paul
Hewitt. It's wrong, of course, or I wouldn't be cackling here.
Since everyone (except me) has seen this before I won't set up the
problem. Hewitt's analysis (if one can call handwaving without
physical reasoning "analysis") is certainly not transparent to me,
and since the result is incorrect for an ideal model, I can only
assume that the error lies in that analysis. As Oren noted the
situation is not analogous to a falling pole. The end of a falling
pole is *rigidly* attached to the rest of the pole. An ideal chain
will not support compression and is also devoid of tension when
freely falling. The only part of the chain which is not freely
falling in this case is the standing part, and it can only exert
forces *upward* on pieces of the chain which are making the
transition between falling and stopping. The gravitational forces
thus can be the only forces acting on the block and on each of the
freely falling links. As Galileo knew, the resulting acceleration of
each of the freely falling bodies is the same, namely g downward.