Excellent educational science gadget: shows not only the pendulum, but also the law of conservation of momentum and energy. Science toys: when you are tired of studying and work, you can stir the ball and hear the click. Excellent educational and scientific gadgets, have their own history of science and explore the important value of physics. Pull one or more balance balls back, release them and the same number of balance balls will swing to the other side. Very suitable for home decorations, office or office decoration accessories etc. The device demonstrates the conservation of momentum and energy through a series of swing balls . Shoot one or more balance balls, release them and the same number of balls will swing to the other side. Very suitable for home decorations, office decoration accessories or office, etc. It is also suitable for birthday gifts and childrens toys. specification: Condition: New Material: Plastic + Iron Color: silver Size: 17x14cm Package Included: 1 x Balance Ball Ornament Notes: 1. Due to manual measurement, please allow 1-2cm error and make sure you do not mind before ordering. 2. Due to the different placement of pictures, colors may have chromatic aberration, please understand.