SAT Subject Physics Practice Question 192: Answer and Explanation

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Question: 192


The circular metal plate has a concentric circular hole. If the plate is heated uniformly, so that the outer circumference of the plate increases by 4 percent, then the circumference of the hole will

A. decrease by 16 percent
B. decrease by 8 percent
C. decrease by 4 percent
D. increase by 4 percent
E. increase by 8 percent

Correct Answer: D


All linear dimensions within the plate—including the radius and circumference of the hole—will increase by the same amount during thermal expansion. (To see that the hole does indeed get bigger, imagine that it was filled with a flat circular plug of metal. This plug would get bigger as the entire plate expanded, so if the plug were removed, it would leave behind a bigger hole.)

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