A mousetrap-powered racer is a contraption that’s designed to operate by the energy of a mousetrap’s spring. A common design that a lot of people do is tie one end of string to the tip of the trap’s snapper arm and then make a loop on the other end so that the string “catches” a hook that is glued to a drive axle. After it is placed over the hook, the string is wound around the drive axle by swiveling the wheels in the direction opposite to the racer’s intended motion. While the the string is wrapped around the axle as the wheels are turned, the mousetrap’s arm comes closer to the drive axle which causes the spring to "wind-up” and gain potential energy -- the energy an object has when it is at rest. Once the catch is triggered the string will start to unravel from the drive axle which makes the wheels spin, and converts the potential energy into kinetic energy -- the energy an object has when it is in motion. Altogether, this project demonstrates how mechanical energy works