How Does a Clock Keep Time Without a Battery?

Imagine a clock as a little robot inside a box. When you wind it up, it stores energy in a spring like a coiled snake. As the spring unwinds slowly, it turns gears that make the hands move, just like walking without running. The more you wind it, the longer it keeps time!

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Examples

Winding your grandfather's clock every morning keeps it running all day long.
A wind-up toy car moves forward because of the spring you twist before letting go.
Pulling a weight down on a grandfather clock makes the hands move without electricity.

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Categories: Technology · Clocks,Mechanics,Timekeeping