Wobbling back to the middle
Why Do Things Vibrate?
Push something springy out of place and it overshoots the middle, again and again.
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Step 1 of 5
Springy things want to return.
Bend a ruler, stretch a string, squash a drum skin. Every one of them pulls back toward its resting shape with a force.
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Step 2 of 5
But they never stop at the middle.
By the time it reaches its resting shape it is moving fast. Nothing removes that speed, so it sails straight past and bends the other way.
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Step 3 of 5
Overshoot after overshoot is a vibration.
The cycle repeats — out, back, past, back — dozens or thousands of times a second. That repeating wobble is what a vibration is.
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Step 4 of 5
Every object has a favourite rate.
Its stiffness and weight set a natural frequency. Tap a wine glass, a tuning fork or a bridge and each rings at its own particular pitch.
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Step 5 of 5
Push at that rate and it grows enormously.
Small pushes timed to match the natural rate add up. That is resonance — how a swing goes higher, and how a singer can shatter a glass.
Friction eventually eats every vibration. That is why a struck bell fades instead of ringing forever.
The short version
Vibration is springiness plus overshoot, repeating — and matching its natural rate makes it grow.
Try it yourself
Hold a ruler over a table edge and twang it. Slide it longer and shorter — the pitch changes with the natural rate.
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