Imagine that now i have a can. I poke a hole at the centers of both the bottom and the cover of the can. Then i tie a rubber band onto the holes that it goes across the tin from the hole at the bottom to the hole on the cover. After that i stick some plasticine onto the rubber band. When i roll the can, it will stop and come back to me. What is the mechanism inside the can that make it stops and comes back? Thank you for answering my question.