Coupled Pendulums & Beats

Energy that swaps back and forth

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

• Coupled oscillators have normal modes with slightly different frequencies.
• Energy swaps between them, fully after 1/(2Δf).
• Two close tones produce beats at the difference frequency.

Steps

1. Two pendulums, one spring
2. How long to hand over?
3. Tune the coupling
4. Hearing it
5. Count the beats
6. Sharp or flat?