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Re: Hewitt

David Abineri wrote:

> Can anyone lend a hand in saying something that might make it easier to
> see the solution to Hewitt's Figuring Physics in the January Physics
> Teacher?
>
> I am having trouble seeing how the acceleration of block B is increasing
> as it falls and how I would explain this to my class. Any insights would
> be welcome. It's a great question!
>
> --
David Abineri dabineri@choice.net

The chain is clearly given to massive.
We can simplify the problem by letting the mass of the blocks go to
zero and ask if the end of the chain will reach it¹s fully extended
position before the d = 1/2 at^2 equation would predict.

I would ask the students to consider what happens to the accumulating
KE as the chain falls.
We heathens would think that the PE into KE process would give the
final link a pretty good kick in the pants since the initial links
are presumed to be at rest.

Also, focus your attention on each link in turn as it is situated at
the bottom of the loop.
That link is being brought to rest by the upward force of the two
strands. The fixed strand isn¹t accelerated (except for the
inevitable stretching of real objects) but the freely falling links
are accelerated as each successive link is brought to rest.




Just because Hewitt sez it, doesn¹t GUARANTEE that it is wrong ;-)





(i¹m waiting for the neigh-sayers to speak up)

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