If you were standing on a cart that was at rest and free to roll (ignore friction) and someone threw a 10 kg ball at you, you would
A) not move if you caught the ball because you are more massive than the ball.
B) roll backward faster if you caught the ball.
C) roll backward faster if the ball bounced off of you elastically.
D) roll backward faster if you caught the ball higher above the ground.

Question

Quizplus · Accepted Answer

According to the law of conservation of momentum, if the ball bounces off of you elastically, it will transfer its momentum to you and the cart, causing you to roll backward faster. This is because the momentum of the system (you, the cart, and the ball) must be conserved. If you caught the ball or caught it higher above the ground, the momentum transfer would be less, so you would not roll backward as fast.

If You Were Standing on a Cart That Was at Rest