SAT Subject Physics Practice Question 259: Answer and Explanation

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Question: 259

30.

A small box slides down a frictionless track in the shape of a quarter-circle of radius R. The box starts from rest at the top of the track, a height equal to 2R above a horizontal surface. At the moment the box leaves the bottom of the track, a ball of the same mass as the box is dropped from the same height at the bottom of the track.

Once the box leaves the bottom of the slide, which of the following statements best describes the motions of the box and the ball?

A. The ball hits the floor at the same time as the box.
B. The ball hits the floor before the box does.
C. The ball hits the floor after the box does.
D. The acceleration of the box is greater than the acceleration of the ball.
E. The acceleration of the ball is greater than the acceleration of the box.

Correct Answer: A

Explanation:

Since both the box and the ball have zero vertical velocity at the moment when they’re released, they’ll both take the same amount of time to fall to the surface. The box’s horizontal velocity at the moment it leaves the track is irrelevant to this question.

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