Rotational Inertia

The rolling race

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Moment of inertia $I = \sum mr^2$: mass far from the axis is harder to spin.
• Rolling objects share energy between moving and spinning.
• In a rolling race, sphere beats disc beats hoop, whatever their mass and size.

Steps

1. Predict the race
2. Race!
3. Moment of inertia
4. Which is easier to spin?
5. A spinning disc
6. Rolling speed