SAT Subject Physics Practice Question 669: Answer and Explanation

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Question: 669

5. Two objects A and B are placed into free fall 14.7 m above the ground at exactly the same time. Object A reaches the ground in exactly 1 second, and object B reaches the ground in exactly 3 seconds. Which of the following is/are true?

I. Object B was thrown horizontally.

II. Both objects were thrown.

III. Neither object was thrown.

A. I only
B. II only
C. I and III only
D. II and III only
E. I, II, and III

Correct Answer: B


The correct answer is (B). Neither object could reach the ground in 1 second unless it was thrown downward. Therefore one of the objects, A, was thrown downward. The other object, B could not have been placed into free fall from rest and taken 3 seconds to reach the ground from a height of 14.7 m because it only takes 1.73 seconds to reach the ground for an object starting from rest. The object that takes 3 seconds to reach the ground must therefore have been thrown upward. This means both objects were thrown.

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