Small Size Newton's Cradle Steel Balance Ball Physics Pendulum The set of balance balls is particularly suitable for the place such as office, desk table,computer table more. . 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. . Pull up one ball and release,only one ball in the other side moves,pull up two,two balls will react, and so on. . When you are sleepless,just move your eyes with the bump of the ball,then you may slowly,slowly falling asleep. . Watching the bump of the ball is a special way to pass the dull hours. . Material:Solid steel ball,Nylon plumb line,ABS plastic frames and base. . Color:The base is Claret-red,the rest are Silver. . Description: Dimension: Approx.9x7.5x9.5CM(LxWxH) . Weight: 79g . Color:As the picture . Package Included: 1 x Newton's Cradle Balance Balls Desk Toy