There is a very common misconception that gravity causes objects to come to rest. Notice that the ball slides up to an equal height on the other side of the hill. The same height also tells you that the GPE is the same on each side of the hill. Whatever energy it starts with at the top is the same it ends with. Notice that in the absence of friction, there is no torque placed on the ball to cause it to rotate.
Friction is responsible for rolling as opposed to sliding.
This simulation assumes there is no friction of any kind. This web site is designed and maintained by Science Joy Wagon and may not be reproduced or redistributed without written permission from Science Joy Wagon. Contact Steve Wirt with comments.