The small-amplitude periods of uniform rectangular compound pendulums, suspended from a corner, are T0=2π2l/3g, where g is the acceleration due to gravity; i.e., the period only depends on the length l of the diagonal, and not on the aspect ratio of the rectangle, so it is the same for a square pendulum and a thin rectangular rod. Rectangular pendulums of a variety of aspect ratios were cut from a sheet of cardboard. A thin pin at one corner, or one quarter along the diagonal, functioned as the pivot. The equipment is simple and readily available, so this can be a take-home experiment with students using their smartphones as stopwatches.

The compound pendulum1 provides an introduction to simple harmonic motion,2 measurement of moments of inertia,3 and large-amplitude motion to study nonlinear oscillations.4 A classic introductory experiment...

Supplementary Material

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