How do analog clocks/watches tick at exactly a second?
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Believe it or not it has to do with the function of a simple pendulum. A heavy weight that is a certain length away from a pivot point. We can determine the rate at which a pendulum will swing back and forth simply through knowing the distance the weight is from the pivot and the force applied to the pendulum to get it swinging. So you use a little math to make a pendulum that will swing with a period of 1 or 2 seconds exactly.
Now we make a device to drive that pendulum. In turn the resistance from that pendulum will regulate the rate at which the device advances. If we measure the number of swings of that pendulum (divided by 2 if it’s a 2 second interval) and then display that output in increments of 60 on a dial, then you have a clock.
Wristwatches take that pendulum concept and turn it on its side. The force of tension from the length holding the weight to the pivot is what forces the weight to swing back the other way. Thus we just need something that can hold tension. So we place a spring inside a wheel of a specific size and weight. In the center of that wheel we place a thin pin (to minimize friction). We send that wheel spinning. As it sounds one way it build tension on the spring until the tension overcomes the force of rotation and sends it back spinning the opposite direction. It changes direction of spin every second. Now we scale down our mechanism we used in the grandfather clock and use this new spinning pendulum to keep the mechanism at a steady 1 second pace.
Now it’s not perfect due to inefficiencies in the system most wristwatches and grandfather clocks can lose a second or two each day. Also we have to keep the spring driving the whole mechanism wound like a wind up toy. However for a first accurate time piece it works well.
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