Balance Balls are a classic desk toy. Also known as Newton's Cradle, the clacking of the steel balls will keep you entertained throughout the day. Pull back one or more of the balls, release them and the same number of balls will swing up on the opposite
How Newton's Cradles Work - HowStuffWorks The toy illustrates the three main physics principles at work: conservation of energy, conservation of momentum and friction. In this article, we'll look at those principles, at elastic and inelastic collisions, and kinetic and potential energy.