The Newton’s Cradle Fridge Magnet takes the familiar desk toy and sticks it on the refrigerator door. With the Newton’s Cradle Fridge Magnet your refrigerator can demonstrate the laws of conservation of mass and energy each time you open and close the door. Watch as its potential energy gets converted into kinetic energy and transfers that kinetic energy all the way down the line. Simply stick it right to your refrigerator, your filing cabinet, your locker, or really anything that’s metal, and start bouncing your balls back and forth immediately.