I have very little knowledge of physics but don’t fully understand how a weight can serve to power a pendulum clock without verging on something like perpetual motion, which I know is of course impossible. How can a pendulum keep swinging almost indefinitely like that? And if a pendulum can use gravity to power itself, why can’t we use gravity to power larger scale devices?
In: Physics
The pendulum itself is just for keeping time; it isn’t the main energy-storage medium for the clock. You’re right in thinking that, if that were all there was to it, the clock would not-so-gradually grind to a halt. After all, a free-swinging pendulum eventually slows down, and it doesn’t have to spend energy driving clockwork.
Instead, there’s a sort of mechanical battery that periodically recharges the bob’s swing. This could be a spring that’s wound daily and, every, say, five minutes is allowed to click one notch out and jolt the pendulum. Or, in some elegant grandfather clocks, there’s a heavy weight that, by ratcheting down a fraction of an inch, boosts the pendulum. When the weight has, bit by bit, fallen to the bottom of its track, it needs to be lifted to the top to recharge.
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