Problem III:
When Swiss people heard the rumor that the moon was made of cheese, they, of course, got the idea that it may also contain holes. Let's assume that the moon does indeed contain a giant hole, and then consider how someone might be able to detect this hole via measuring the difference in gravitational acceleration at the moon's surface, near and far from the hole:
Suppose the moon is an otherwise uniform density sphere which has an empty spherical cavity located halfway between the center and the surface, as shown below in the cross-sectional sketch. Given a mass density, p, and the relative radii, Rmoon=4Rcavity, what is the ratio of the acceleration due to the moon's gravity at the moon's surface nearest to (point A) and furthest from (point B) this hole? In terms of the parameters given above (and also Newton's gravitational constant), what are the escape velocities at these two positions at the moon's surface, nearest to and furthest from the hole? Note: here, please disregard the gravitational pulls of the earth and the sun.
4 - Rcavity = Rmoon
I
B
A
Ratio of accelerations g@/g@B?
Escape velocity at point A?
Escape velocity at point B?