SAT Subject Physics Practice Question 161: Answer and Explanation

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Question: 161

7. Which quantity can be expressed in the same units as impulse?

A. Displacement
B. Velocity
C. Acceleration
D. Linear momentum
E. Kinetic energy

Correct Answer: D


Impulse is equal to force multiplied by time, so its units are N-s. Because 1 N = 1 kg-m/s2, we see that 1 N-s = 1 kg-m/s, which we immediately notice is the same as the units of mass (kg) times those of velocity (m/s), and mv is linear momentum, D. You may also have remembered the impulse–momentum theorem, which says that the impulse delivered to an object is equal to the resulting change in its linear momentum. Since impulse gives the change in linear momentum, it must be true that impulse can be expressed in the same units as linear momentum.

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