A myriad range of natural phenomenon, from harmony and dissonance in music to interactions between surface and body waves during seismic events, produce "beat” frequencies. This experiment demonstrates the beat effect in the interaction of two identical oscillating pendulums coupled by a light spring. The effect is due to the coupled pendulums swinging between the system's two normal modes of oscillation. Whereas these two normal modes can both be modeled as single harmonic oscillators, their sum cannot. Such a sum, given certain initial conditions, causes the transfer of kinetic energy between the two pendulums. The period of this transfer is studied as its beat frequency. The aim of this experiment is to both theoretically analyze and empirically examine these frequencies.

Coupled Identical Pendulums