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Re: Hewitt blew it again



I received my January Physics Teacher today, a very long delay.
I've reread Hewitt's "Answer" and I find it completely
unsatisfactory. If Hewitt is correct, his answer should end at
"Block B hits the floor first." Nothing he says after that is
the least bit illuminating; he hasn't conveyed the concept to
me, at least, and I don't think I'm the least teachable person

Jack Uretsky suggests that the catenary profile of the chain is
important to this putative effect. I will try the experiment
again, but I intended to perform it in a different manner, with
the chain initially belayed below the drop point. This will
give me double the height that can be had with Hewitt's setup.
I will use a video camera (1/60 s per field) and an exposure
time of 1/10,000 s to do the timing. I have not been able to
come up with a simple method of starting the ball and the end
of the chain at the same time, and I'm open to suggestions. I
will, of course, drop the several times.

To achieve symmetry I have obtained a plastic chain and a steel
ball, the complement to Chuck Britton's apparatus. The catenary
shown in Hewitt's cartoon has an aspect ratio of about four. I
used a much skinnier catenary in my first experiment. I thought
the result would be insensitive to that parameter, as the case
of the bungee must surely be so.

Any suggestions? I use a 500 W quartz halogen lamp to take
video at 1/10,000 s.

Leigh