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

On 10/04/2010 02:12 PM, Fakhruddin, Hasan wrote:
I believe the radius will decrease due to the planets pull on the
particles of the ball, directed toward the center of the planet. So
Choice C.

Not a chance.

The only parts of the planet that could have produced such
an effect were removed when you created a cavity big enough
for the ball to sit in.

It's a famous result, published by Sir Isaac himself. The
field inside a spherical shell is zero.


Nitpickers note: This assumes Newtonian gravity, symmetry,
and other conventional simplifications.