Question

Principle on which most of clocks work

Answer 1

At its most basic, it uses the principle of the pendulum. This is how the earliest clocks worked, after Galileo noted that the amount of time that it takes for a pendulum to make a complete cycle is the same regardless of how far it swings back and forth. It’s entirely a function of the mass of the pendulum and the length of the arm. Thus, it is possible to tweak those two parameters to make the pendulum swing in exactly one second (or five seconds, or whatever time unit you want). A Metronome uses the same principle, but allows you to adjust the “length” to whatever time unit you want.

The Pendulum uses Gravity to act as a “restoring force”, but that makes the pendulum dependent on its orientation relative to gravity. Thus, a pendulum based clock can’t be tilted or moved easily.

Watches took this concept, replaced “gravity” with a spiral spring (the hairspring), and turned the pendulum into a circle. While the hairspring isn’t quite as consistent as gravity, it’s close enough that even a hundred years ago, we were able to tweak them to attain accuracy within 5 seconds a day.

Answer 2

I think it is simple Harmonic motion which is the main Principle behind working of a clock or a simple pendulum.