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Short · Clocks

Why do grandfather clocks have such long pendulums?

A pendulum's swing time depends on its length, not its weight. Four times the length gives twice the time, so a one-meter pendulum ticks once a second.

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Narrated · 35 seconds · captions includedDownload the film

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Transcript

Why do grandfather clocks have such long pendulums? A pendulum's swing time depends on its length, and almost nothing else. Not its weight. Not even how wide it swings, as long as the swing stays small. Now make the pendulum longer. The swing slows down. Four times the length, twice the time. At about one meter, each swing takes one second, just right for ticking a clock's second hand. That's a big reason the case is so tall. Try it yourself at Explainer Tools dot com.