12.64
A dumbbell has a mass m on either end of a rod
of length 2a. The center of the dumbbell is a distance
r from the center of the Earth, and the dumbbell is
aligned radially. If r≫a, the difference in the
gravitational force exerted on the two masses by the Earth is
approximately
4GmMEa/r3.
(Note: The difference in force causes a tension in the rod
connecting the masses. We refer to this as a tidal
force.)
Suppose the...