A2L Item 153

• Description: Identify which vehicle receives the largest impulse during a collision.
• Goal: Hone the concept of impulse
• Source: UMPERG-ctqpe80
• Keywords: Impulse, Mechanics, Reasoning

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The question for students:

A MOVING car collides with a STATIONARY truck. Which of the following statements is true about the magnitudes of the impulse on each due to the other?

1. The impulse on the car is larger than the impulse on the truck.
2. The impulse on the truck is larger than the impulse on the car.
3. The magnitudes of the two impulses are equal.
4. Answer depends upon circumstances of the collision.

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Commentary for teachers:

Answer

(3) The 3rd law requires that the impulses be equal. Even students who understand the 3rd law have difficulty realizing that the magnitude of the impulse on two interacting bodies is the same. Many students, however, do not understand impulse enough to recognize the association. Others do not read the problem carefully enough and answer with regard to ALL the forces, not just the one due to the other vehicle.

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