### Homework Pencast Chapter 4.7 Problems 5-9

5. A bowling ball (mass = 7.2 kg, radius = .11m) and a billiard ball (mass = .38 kg, radius = .028 m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the other? Answer in nN (nano Newtons).

6. The drawing (not to scale) shows one alignment of the sun, earth, and moon. The gravitational force FSM that the sun exerts on the moon is perpendicular to the force FEM that the earth exerts on the moon. The masses are:

mass of sun = 1.99 x 10^{30} kg

mass of earth = 5.98 x 10^{24} kg

mass of moon = 7.35 x 10^{22} kg.

The distances shown in the drawing are:

r_{SM} = 1.50 x 10^{11} m

r_{EM} = 3.85 x 10^{8} m.

Determine the magnitude of the net gravitational force on the moon.

7. Mars has a mass of 6.46 x 10^{23} kg and a radius of 3.39 x 10^{6} m.

7a. What is the acceleration due to gravity on Mars?

7b. How much would a [68]-kg person weigh on Mars?

9. A space traveler weighs [640] N on earth. What will the traveler weigh on another planet whose radius is three times that of the earth and whose mass is twice that of the earth?