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How does a pendulum clock work?
Answer 1:

All clocks need some part of them that perform a regular action that takes a very predictable amount of time. Some clocks have springs and gears that perform this tasks, and a lot of clocks have quartz crytals.

A pendulum clock uses a weight swinging back and forth to provided a regular action which can drive the rest of the clock. The reason a pendulum works well for this has to do with the physics of how a pendulum swings. More specifically, the amount of time it takes for a pendulum to complete one full swing does not depend at all on it's mass, or the amplitude of its swing, but only on the length of the pendulum and gravity. Since gravity is pretty constant on the surface of the earth, and the length of the pendulum doesn't change, the length of time it takes for a pendulum to complete a full cycle is very reliable.

Because the pendulum's frequency doesn't depend on the height to which the pendulum rises, this means that even if the pendulum looses energy and swings lower and lower, it timing will remain intact.


Answer 2:

A pendulum has a natural frequency at which it swings back and forth. I do not recall the exact physical details of what causes the period of swing, but because it is periodic, it is possible to measure time with it.



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