Rotational Energy

Torque, spin-up and flywheels

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

• $\tau = I\alpha$ is Newton's second law for rotation.
• Rotational kinetic energy: $\frac12 I\omega^2$; for a solid disc, $\frac14 m v_\text{rim}^2$.
• A flywheel’s storage is limited by how fast its rim can go before bursting.

Steps

1. Newton’s law for spinning
2. Energy of spinning
3. Design a flywheel
4. Energy per kilogram
5. Hollow or solid?
6. Spinning Earth