16.

Mercury rotates on its axis every 58.65 Earth days. Its mass is just 5.5% the mass of the Earth. How far from the center of Mercury could a satellite make an orbit that is synchronous with that planet?

1. 2.4x10⁸ m
2. 1.7x10⁸ m
3. 7.9x10⁸ m
4. 5.3x10⁸ m

17.

A point mass (0.5 kg) is at rest 0.5 m from the end of a very dense, very thin rod. The mass of the rod is 100000 kg in mass and is 70 m in length. What is the magnitude of the gravitational force exerted on the point mass?

1. 6.3x10^-8 N
2. 9.0x10^-8 N
3. 2.9x10^-8 N
4. 9.5x10^-8 N

18.

A small mass (m = 0.25 kg) is released from rest within and near the left side of a large spherical shell of material. Which direction will the small mass accelerate?

1. left
2. toward the center
3. right
4. It will not move

19.

The same small mass from question #18 is now released from rest 1000 m from the center of a shell of material. The shell has a radius of 500 m and a mass of 10000 kg. A second shell, whose center is 2500 m from the center of the first shell, has a radius of 500 m and a mass of 5000 kg. The centers of the small mass and both shells are along a straight line with the small mass in between the shells. Toward which shell will the small mass begin to move?

1. Toward shell 2
2. Toward shell 1
3. The mass is equilibrium. It will not move.
4. No enough information given

20.

Now the small mass from question #18 finds itself inside a solid sphere (m = 1000000 kg and R = 2000 m). If the small mass is halfway between the center of the sphere and the surface, determine its weight.

1. 2.1x10^-12 N
2. 0.5x10^-12 N
3. 4.9x10^-12 N
4. 6.0x10^-12N