1. Which statement is true about the gravitational forces between two masses m1 and m2?

a. They can never be equal regardless of the masses.

b. They are equal only when the two masses are equal.

c. They form an "action and reaction" pair in accordance with Newton's Third Law.

d. Both act on the same body. e. none of these

2. The radius of Earth is about 6400 km. How far upward from the surface would a body feel a value of g about half of that on the surface of Earth?(Pick the best response) a. 3200 km b. 4800 km c. 6400 km d. 12 800 km

3. Which of the following planets orbits the Sun with the slowest speed? a. The closest b. The farthest c. Earth d. All orbit with the same speed.

4. If the distance between a spacecraft and Jupiter increases by a factor of 2 and the mass of the satellite is decreased by a factor of 2, the magnitude of Jupiter's gravitational field strength at the position of the spacecraft changes (a) by a factor of .5 (b) by a factor of 0.25 (c) remains the same (d) by a factor of 2

5. 7. Two satellites, S1 and S2, are in circular orbits around a planet. Satellite S2 has three times the orbital radius of satellite S1. What is the ratio of the speed of S2to that of S1 (S2:S1)? A. 1:1 B. 1:3 C. 3:1 D. 1:9