Name: ______________________

Quiz 9

05/13/2005

Ch. 12

1)
Assume
that you, the earth, and the moon are the only objects in the universe and the
earth and the moon are in their current locations. (note: Express your answers in terms of some or all of the
following: mass of the earth Me, mass of the moon Mm, the distance between the
centers of earth and the moon Dme, your mass m, and the gravitational constant
G.)

a)
Find
the zero force point, the place in the universe (not infinity) where you will
experience no force.

b)
What
is the gravitational potential energy at the zero force point, assuming the
gravitational potential is zero at infinity?

c)
What
is the gravitational potential energy at surface of the earth Re, assuming the
gravitational potential is zero at infinity?

d)
What
is the work required to bring you from infinity to the zero force point?

e)
If
you started at surface of the earth a distance Re from the center of the earth
what speed would you need to just reach the zero force point?

2)
You
are in a circular orbit around the moon at a radius of 1.5 times the radius of
the moon. The radius of the moon is 1.738 x 10^{6} m and the mass of the moon is 7.35x10^22 kg.

a)
What
is the period of your orbit?

b)
What
is your speed?

c)
What
is your total energy?

d)
Which
of the previous answer a-c would change if you orbit were an ellipse?