SAT Subject Physics Practice Question 561: Answer and Explanation
2. A golf ball is placed inside an unmounted tire, which is then rolled down a long hill. Identify the statement(s) that best describe the situation while the tire and golf ball are rolling down the hill.
I. The centripetal force on the tire operates in the same direction as the centripetal force on the golf ball.
II. The centripetal force acting on the tire is opposite the centripetal force acting on the golf ball.
III. The centripetal force acting on the golf ball is equal to the centripetal force on the tire.
A. I only
B. II only
C. I and III only
D. II and III only
E. I, II, and III
Correct Answer: A
The correct answer is (A). Centripetal force is also called the center-seeking force. Both the tire and the golf ball roll about their centers of mass, which are located in the center of the objects. The centripetal force for the two cannot be equal because the radii of the two objects are different, yet they roll with the same tangential velocity.