Question

50. It is easier on your car if you stop by plowing into a deep snow drift than if you stop by plowing into a brick wall (ouch). This is because...

A. momentum change is less for the snow drift.

B. impulse is greater for the brick wall.

C. momentum is less for the brick wall.

D. longer stopping time for the snow drift.

51. When a running football player “throws” his right foot down and behind him, as in this sketch, what happens in reaction is:

A.The ground pushes up and forward.

B. The ground exerts no force on him.

C. Counter-rotational torque applies.

D. He begins to fall backward.

Answer 1

Answers:

50. (D) longer stopping time for the snow drift.

If the car is stopped by plowing into snow, the time required to stop the car is more. The larger time thus decreases the force the snow exerts on the car. Therefore, the car is easier to stop.

In case of the brick, the car stop suddenly. Thus more force is exerted on the car.

51. (A) The ground pushes up and forward.

When the footballer throws his right led down and behind, he leg exerts a force on the ground which is the Action force. Thus the ground exerts a Reaction force up and forward.