Demos: 1S-24 Resonance Ball Spring

A heavy metal ball suspended from a spring is attached to an eccentric cam on the shaft of an electric motor. The turning of the cam causes a forced oscillation of the spring-mass system. When the frequency of the driving mechanism matches the resonant frequency of the spring-mass system, large oscillations ensue.

Directions: First pull the weight down by hand and release. The system will oscillate at its resonant frequency. Then turn on the motor and start at a very slow speed well below the resonant frequency (or alternatively, start a higher speed and come down). Some erratic oscillations will occur, but these are mostly damped out. As the driving frequency reaches the resonant frequency, large oscillations start to build up.

Suggestions for Presentation: Nothing special here. After presenting the case for resonance, remind students that oscillating systems have natural vibrating frequencies and that if energy is fed into the system at its resonant frequency, large amplitude oscillations result. [Compare with Demo 1S - 23]

Applications: Out of balance auto tires, excessive vibrations in machinery, etc.

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Last Updated: May 9, 2016 11:44 AM