Tidal locking is what makes the Moon rotate about its own axis at ...

[neverstopbelieb]

Tidal locking is what makes the Moon rotate about its own axis at the same rate that it revolves around Earth.
 
  Using as a model of a moon two identical masses of mass m connected by a light rod, explain how the forces on the masses would tend to keep this satellite in a fixed orientation.

Question 2

A circular loop of wire of radius 0.50 m is in a uniform magnetic field of 0.30 T. The current in the loop is 2.0 A. What is the magnetic torque when the plane of the loop is perpendicular to the magnetic field?
 
  A) zero
  B) 0.41 m  N
  C) 0.47 m  N
  D) 0.52 m  N
  E) 0.58 m  N

[C.mcnichol98]

Answer to Question 1

Suppose that the masses are oriented so that the rod is along a radial line from the planet. The forces on the two masses are unequal, but they are lined up, so there is no tendency to turn. If the rod is turned a small amount, the mass nearer the planet is attracted with a larger force, so there is a net torque directed so as to orient the satellite the way it was originally. If the rod is turned through 90, the torques are again in equilibrium, but this is an unstable equilibrium because a small displacement away from that position will produce a torque in the same direction as the rotation of the rod.

Answer to Question 2

A