SAT Subject Physics Practice Question 583: Answer and Explanation

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Question: 583

9. A pile driver is raised to a height of 25 m in 10 seconds. It is released and allowed to fall onto a piling. Although guided by a set of rails, the pile driver essentially is in free fall after its release. Which of the following is/ are correct?

I. The power input equals the power output.

II. The PE in equals the KE out.

III. The KE in equals the work out.

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

Correct Answer: D

Explanation:

The correct answer is (D). The potential energy transforms into kinetic energy, or the pile driver falls. At the end of the fall, all the kinetic energy the pile driver has is converted into frictional work to drive the post into the ground.

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