Driven Tuning Fork - Physics Demonstrations - Driven Tuning Fork | Physics Undergraduate Labs

Purpose

Demonstrates mechanical resonance by driving a 256 Hz tuning fork with a speaker at various frequencies. Ping pong balls resting against the tines bounce vigorously at the resonant frequency and stop within a few tenths of a Hz off-resonance, making the sharpness of the resonance peak visually dramatic.

Tuning fork in wooden base at resonance: orange and white ping pong balls suspended from a horizontal rod are motion-blurred as they bounce off the vibrating tines. Speaker visible at base of fork, signal generator at right.

Two tuning forks in wooden bases side by side, with orange and white ping pong balls hanging still on strings from a horizontal rod between the tines of the left fork. The right fork has no balls.

Figure 1: Tuning fork at resonance (256 Hz). The ping pong balls bounce vigorously off the vibrating tines, appearing blurred in the photo. The small speaker directs sound into the open end of the wooden resonator box.

Figure 2: Two tuning forks with the full apparatus. The ping pong balls hang at rest against the tines of the left fork when the driving frequency is off-resonance.

Resonant Tuning Fork Set

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Ping Pong Balls on String

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