Defying Gravity

Why tops precess

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Gravity’s torque on a spinning gyroscope swings it sideways: precession.
• Precession rate $\Omega = mgr/(I\omega)$.
• Faster spin means slower precession.

Steps

1. Sideways, not down
2. Torque turns the arrow
3. Spin faster
4. Compute the precession
5. How fast it precesses
6. The extra wobble
7. Reverse the spin