Fun Science: The Newton’s cradle is a device that demonstrates conservation of momentum and energy via a series of swinging spheres. If one ball is pulled away and is let to fall, it strikes the first ball in the series and comes to nearly a dead stop. The ball on the opposite side acquires most of the velocity and almost instantly swings in an arc almost as high as the release height of the last ball. This shows that the final ball receives most of the energy and momentum that was in the first ball. But have you wondered why, when two or more balls are raised on one side and is let to fall, a corresponding number of balls will swing up on the other side? How does the balls on the other side “know” how many balls were raised? Why doesn’t all the energy gets transferred to the very last ball? Turns out, the explanation is very complex (definitely out of syllabus). Read here for more: http://en.wikipedia.org/wiki/Newton%27s_cradle