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Re: [Phys-l] Clarification: A ball at the center of a planet

But since our instructors already HAD their PhD's - we were just playing out this same game.

Are you concerned about General Relativity or Gauss's Law for gravity.

GenRel plays a hand if the 'Free Space' scenario still has any Grav PE due to the planet.

If not - it 'just' seems to be a gravitational Gauss's Law exercise.

At 12:38 PM -0500 10/4/10, Rauber, Joel wrote:
They probably did give their instructors ulcers. I wonder if that is a pre-condition for wanting to get your Phd in Physics.


Alright folks, Here is a little modification:

A solid elastic rubber ball is a perfect sphere of radius r in free
space. A solid homogeneous spherical massive run away planet also in
free space has a spherical cavity formed at its center. The cavity is
much larger than the ball and has vacuum in it. The ball is now
transported to the center of the planet. Its radius now is
(A) > r
(B) < r
(C) = r

(now come on....don't ask me to define free space)

How did you guys ever take any exam without giving your instructor

> 'Burp'....excuse me; I just took Alka-Seltzer!