How does a pendulum keep swinging?

No, it's not perpetual. Like any machine, there are frictional and air drag losses.
In a grandfather clock, the purpose of the weights is to provide a force to supply enough "push" on each oscillation of its pendulum (as well as drive the hands), to offset or exceed those losses. It then swings in a constant arc length.
 
Pendulum clocks have a mainspring or a weight hanging from a string around a drum. The spring unwinds or the weight moves lower when it gives a small nudge to the pendulum with each swing.
 
Momentum, it uses it's own weight. Gravity brings it down, but it's heavy enough to rise up on the other side. Then coming back down, and so on. Probably has something to do with the shapes balance too.
 
Back
Top