1.Which of these follows from Kepler’s laws of planetary motion?
A. Objects attract each other with a force proportional to the product of their masses.
B. All planets move in circular orbits.
C. Planets closer to the sun have lower orbital speeds.
D. A satellite will speed up as it gets closer to the much more massive object it orbits.
2. Which of these is correct about the moon’s motion around the earth?
A. The moon is in free fall.
B. Centrifugal force acting on the moon balances the force of the earth’s gravity.
C. The moon exerts no gravitational force on the earth.
D. There is no gravity acting on the moon because it is in orbit.
3.The force of gravity between any two ordinary objects on the earth is __________.
A. always downward
B. stronger when closer to the earth
C. stronger if the objects are closer to each other
D. stronger than the force of gravity from the earth