Chapter 8, Problem 33A

The example in the previous question can be explained in terms of momentum conservation and in terms of Newton’s third law. Assuming you've answered it in terms of momentum conservation, answer it also in terms of Newton’s third law (or vice versa if you answered already via Newton’s third law).

To determine

To identify: Whether person J will end up rolling backward.

Answer to Problem 33A

Person J will not end up rolling backward.

Explanation of Solution

Introduction:

According to Newton’s Third Law of Motion, every action has equal and opposite reaction.

It is given that person J throws a ball horizontally while standing on roller skates. When a ball is thrown from the rest position then it will produce a jerk to the arm. Because of the recoiling action, person J will move backward. If he throws the ball and at the same time tries to stop the action of the arm, which was produced because of the recoiling action of the ball, by catching the ball itself then the ball will not move. Perhaps, person J will remain at rest too. Thus, once force is provided to the ball, it will move and produce a recoiling reaction to person J’s arm. Thus leading it to move backward.

Conclusion:

Thus, person J will not move backward.