TA: Tomoyuki Nakayama
Monday, March 29
th
, 2010
PHY 2048: Physic 1, Discussion Section 3081
Quiz 8 (Homework Set # 11)
Name:
UFID:
Formula sheets are not allowed. Calculators are allowed. Do not store equations in your calculator.
You need to show all of your work for full credit.
________________________________________________________________________________
Assume a planet is a uniform sphere of radius
R
and mass M that (somehow) has a narrow radial
tunnel through its center. Also assume we can position an apple of mass m anywhere along the
tunnel or outside the sphere. Let
F
R
be the magnitude of the gravitational force on the apple when it
is located at the planet’s surface.
a) How far from the surface is there a point where the magnitude of the gravitational force on the
apple is (1/3)
F
R
if we move the apple away from the planet.
Let r be the position of the apple measured from the center of the sphere. Since r>R, the sphere
exerts force on the apple as if all of its mass were concentrated at the center. We have
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 Fall '08
 Field
 Physics, Mass, Work, General Relativity, Gravitational constant, Gravitational field

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