Practice question · Multiple choice
A child on a swing pumps their legs in time with the motion and the amplitude grows enormously. Which principle is being exploited?
Hints
- Try pumping at random times. Why does that not work?
- Ask what makes small repeated pushes add up rather than cancel.
Show the answer
C. Resonance, since energy added at the natural frequency accumulates
Why
Timing is everything: pushes delivered at the natural frequency add coherently, and mistimed ones partly undo the previous ones. The same principle tunes a radio and collapsed the Tacoma Narrows bridge, which is why soldiers break step crossing one.
Practise Oscillations and Periodic Motion
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