Twin Pendulums - Physics Demonstrations - Twin Pendulums | Physics Undergraduate Labs

Purpose

Demonstrates that the period of a simple pendulum is independent of mass. Two pendulums of equal length but different masses remain synchronized over many swings, directly testing $T = 2\pi\sqrt{L/g}$ and challenging the common misconception that heavier objects oscillate differently.

Two pendulums hanging from a horizontal rod between two tall bench clamp stands, with black nylon string looped over ring clamp hooks and brass mass hangers at the bottom; a blue PASCO mass set sits on the bench

Close-up of the horizontal rod showing three ring clamps with hooks and thumbscrews; the center clamp holds the string midpoint, and the two outer clamps serve as adjustable pivot points

Figure 1: The twin pendulum apparatus: a single string threaded through a center ring clamp and draped over two outer ring clamp hooks, with mass hangers suspended from each end. The PASCO mass set provides interchangeable masses.

Figure 2: Detail of the three ring clamps on the rod. The center clamp anchors the string; the outer clamps act as pivots and can be repositioned to fine-tune pendulum length for period matching.