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. 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.
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