Purpose: Demonstrate transformations between gravitational potential energy and rotational kinetic energy.
Description: Used as a large-scale yo-yo, transformation of energy can easily be observed by a large class. Wind the string around the small spool radius, hold with the axis horizontal, and release. The initial gravitational potential energy is converted primarily into rotational kinetic energy, with a lesser amount of translational kinetic energy, as the device moves downward, with conversion back to gravitational potential energy after the spool reaches its minimum position and moves back upward.
