Newton's Cradle Balancing Balls STEM Desktop Home DecorSee before your eyes as the Newton Balls transfer fall and transfer weight across the gadget. Drop one ball or two balls. You can see the energy transfer in such an astounding way! The pendulum balls show the conservation of momentum and energy, creating perpetual motion. These swinging kinetic balls are perfect addition to your office desk decoration accessories or teaching tool at schools. Comes in a retail box.