Three metal balls roll back and forth. When rolled one way all three balls roll side by side. When rolled the other way one ball rolls ahead of the other two. Students are challenged to explain why.

A set of four gray disk with the same radius and width, but with differing mass distributions.

Torsion pendulum inertia

The chair can be assembled with a large spring (under the seat) connected such that the chair executes simple harmonic motion about an equilibrium position. The period of oscillation depends on the moment of inertia of the chair plus the moment of inertia