Re: pinhole text errors and mine shafts

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From: Paul Doherty (pauld@exploratorium.edu)
Date: Wed Sep 22 1999 - 13:59:50 PDT 

Message-Id: <l0311071fb40ef3314de4@[192.174.2.173]>
Date: Wed, 22 Sep 1999 12:59:50 -0800
From: Paul Doherty <pauld@exploratorium.edu>
Subject: Re: pinhole text errors and mine shafts

Hi Lou

You remember right.
However when you jump into the hole in the earth, the mass of the earth in
the shell of greater radius than your current position exerts no force on
you. Only the mass in the sphere between you and the center counts as the
mass in the equation. Thats why the force of gravity on you goes linearly
to zero at the center of the earth. The linear decrease of force with
distance is what you get from a spring. So jumping into a hole produces
simple harmonic motion!

Paul Doherty

Paul "But it is more complicated than that!" Doherty,
Senior Staff Scientist, The Exploratorium.
pauld@exploratorium.edu, www.exo.net/~pauld

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