Pull one of the balls on the side and then let it go!
Repeat the experiment, so that you pull two or three balls!
The ball stops after colliding with the one next to it, and the ball at the other end of the row swings, then the same thing happens backwards ... If we try with more balls, at the end of the row as many balls swing as we pulled at the beginning.
The phenomenon can be basically explained by the laws of conservation of energy and conservation of momentum.
The process does not last forever, because in that case we would have invented the perpetuum mobile! Many have tried to do it, without success. Thanks to the loss of energy (without any resource of energy from the outside) moving stops after a certain period of time.
