Parametric OscillationsHardQuestion 31190
Question
A child pumping a swing increases amplitude by:
- AApplying continuous horizontal force
- BPeriodically changing effective pendulum length at twice the swing frequency (parametric resonance)Correct
- CPushing at resonant frequency always
- DAdding mass to swing
Correct answer
Periodically changing effective pendulum length at twice the swing frequency (parametric resonance)
Explanation
Standing/squatting on a swing changes its effective length at 2f (twice per cycle). This is parametric resonance — energy is pumped into the oscillator by modulating a parameter.