Chapter 5, Problem 15TE

Michael throws a ball horizontally while standing on roller skates. He rolls backward with a momentum that matches that of the ball. Will he end up rolling backward if he goes through the motions of throwing the ball, but instead holds onto it? Explain.

To determine

Whether Michael end up rolling backward or holds on the roller skates.

Answer to Problem 15TE

Michael remains in same position as momentum remains constant.

Explanation of Solution

Michael stands on the skates, so he does not possess a momentum. But, if no momentum is imparted to the ball, no oppositely directed momentum will be imparted to the thrower.

When the Michael starts throwing the ball, he starts recoiling backwards, at the end of the throw when he stops the motion of your arm and holds onto the ball, the motion of the Michael also stop. The position of Michael may change a little, but he ends up at rest. No momentum given to the ball means no recoil momentum gained by Michael. In this condition, the total momentum remains constant.

Conclusion:

Therefore, Michael remains in same position as momentum remains constant.