SHINA Newton's Cradle Steel Balance Ball Physics Science Pendulum Desk Fun Toy Gift 100% Brand New and High Quality The set of balance balls is particularly suitable for the place such as office, desk table, computer table etc. It is a best and useful gift for children to arouse his/her interest in physics. Not only demonstrates a pendulum, but also shows the Laws of Conservation of Momentum and Energy. Friction and damping effects are also observed.