Coupled Pendulum
Definition
Two pendulums linked by a spring that trade energy back and forth — set one swinging and the other gradually takes over, then hands it back.
Technical definition
Two oscillators with a coupling term exchange energy at the beat frequency |ω₁ − ω₂|; the system has two normal modes (in-phase and out-of-phase) with split frequencies.
Example
Two metronomes on a shared board synchronize — the tiny coupling through the board locks them into the same rhythm.
Common confusion
The energy transfer is not magic or air resonance — it travels through the coupling (the spring or board). Remove the link and each pendulum swings alone.