Question

A student's life was saved in an automobile accident because an airbag expanded in front of his head. If the car had not been equipped with an airbag, the windshield would have stopped the motion of his head in a much shorter time. Compared to the windshield, the airbag:
(A) causes a much smaller change in momentum
(B) exerts a much smaller impulse
(C) exerts a much smaller force
(D) causes a much smaller change in kinetic energy
(E) does much more work

Answer 1

Answer:

(C) exerts a much smaller force

Explanation:

The change in momentum  in the accident is the same with or without airbags. Recall the impulse equation:

$I=F\Delta t=\Delta p(1)$

Where, F is a constant force and p is the momentum.

The airbag allows student to experience the same impulse in  a longer time interval. So, if the impulse is the same but the time interval $\Delta t$ is greater, the force exerted on the  student has to be smaller, as equation 1 says.