SAT Subject Physics Practice Question 228: Answer and Explanation

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Question: 228

74. Why do baseball catchers wear mitts rather than just using their bare hands to catch pitched baseballs?

A. The impulse delivered to the catcher’s hand is reduced due to the presence of the mitt.
B. The force on the catcher’s hand is reduced because of the increased area provided by the mitt.
C. The baseball’s change in momentum is reduced due to the presence of the mitt.
D. The force on the catcher’s hand is reduced because the mitt increases the time of impact.
E. The force on the catcher’s hand is reduced because the mitt decreases the time of impact.

Correct Answer: D

Explanation:

The impulse delivered to the ball is equal to the ball’s change in momentum, and the presence of the mitt does not change this, eliminating A and C. The extra area may decrease the pressure on the catcher’s hand, but not the force (eliminating B). The padding of the mitt causes the time during which the ball comes to a stop to increase (just as an air bag increases the time it takes for an automobile passenger involved in an accident to come to a stop), which decreases the magnitude of the ball’s acceleration (since a = Δvt). A decrease in the magnitude of the acceleration means a decrease in the magnitude of the force (since a = F/m).

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