Slinky

A Slinky is a coil-shaped toy made of metal or plastic that can stretch and return to its original shape. It operates on basic physics principles, mainly gravity and momentum, which allow it to perform tricks like "walking" down stairs or bouncing end-over-end. When you hold one end and let the other hang downward, gravity pulls the weight, causing the coil to stretch and then snap back, transferring energy along its length. Its simple yet fascinating motion illustrates concepts of wave mechanics and energy transfer, making it both entertaining and educational.