Wheel Race

Principle of Science: Angular Momentum, Rotational Moment of Inertia

Two ramps are connected by a level section of track. Race the two wheels by holding the two wheels at the top of the ramps and letting go. Both wheels weigh the same, but their weights are located in different places: one has weights near the rim (heavy rim) and the other has weights near the center (light rim). Which wheel is fastest? Which one goes furthest up the other side?

The wheels start with the same potential energy because they start at the same height. As a result, they go the same distance up the other side, but at different speeds. The heavy rim takes a while to speed up but seems to keep going at a steady pace even as it travels uphill on the other side. The light rim speeds up very rapidly; however, as it travels up the second ramp, it slows just as quickly.

Racing bicycles have lightweight rims – these speed up quickly. Flywheels on machinery have heavy rims that take time to speed up, but store energy and stay spinning for longer.