SAT Subject Physics Practice Question 246: Answer and Explanation

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Question: 246

17. A lightweight toy car crashes head-on into a heavier toy truck. Which of the following statements is true as a result of the collision?

I. The car will experience a greater impulse than the truck.

II. The car will experience a greater change in momentum than the truck.

III. The magnitude of the acceleration experienced by the car will be greater than that experienced by the truck.

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

Correct Answer: C


By Newton’s third law, both vehicles experience the same magnitude of force and, therefore, the same impulse; so I is false. Invoking Newton’s second law, in the form impulse = change in momentum, we see that II is therefore also false. However, since the car has a smaller mass than the truck, its acceleration will be greater in magnitude than that of the truck, so III is true.

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