SAT Subject Physics Practice Question 624: Answer and Explanation
5. Two spheres are placed into free fall from rest. Sphere B has a mass three times larger than sphere A. Which statement(s) correctly explains the situation?
I. Sphere B falls faster.
II. Sphere B has more momentum when the two reach the ground.
III. Both spheres reach the ground with the same kinetic energy.
A. I only
B. II only
C. I and III only
D. II and II only
E. I, II, and III
Correct Answer: B
The correct answer is (B). Both spheres fall from the same height. This means the objects are in free fall, so their accelerations are the same. Sphere B has more mass than sphere A, which gives sphere B more momentum and more kinetic energy when the two spheres reach the ground.