* *  Newton's Cradle Balance Balls Toy, Physics Science Pendulum Wave Balls Educational Kits Desk Fun Toy Gift for Kids Adults.* *      * * HOW TO PLAY -- * * * Pull back one or more of the balance balls, release them and the same number of balls will swing up on the opposite side.    * * EDUTAINMENT -- * * * Suit for both kids and adults, they could experience the fun of mechanics in the process of playing this fun gadget and explore significant values of physics.    * * PERFECT DECORATION * * * Not only a toy, but also a great desk ornament for home or office. Also good for birthday gift and kids toy.     * * RELEASE THE PRESSURE * * * Perfect for releasing the pressure boring time, When you are tired of studying and working, you can stir the ball to hear the clinking sound to ease.      * * EDUCATIONAL SCIENCE GADGET  * * * Not only demonstrates a pendulum, but also shows the principles of kinetic energy and conservation of momentum.  * Friction and damping effects are also observed.