Bob (physics)

Although a pendulum can theoretically be any shape, any rigid object swinging on a pivot, clock pendulums are usually made of a weight or bob attached to the bottom end of a rod, with the top attached to a pivot so it can swing.

The advantage of this construction is that it positions the centre of mass close to the physical end of the pendulum, farthest from the pivot.

Moving it up shortens the pendulum, making it beat more quickly, and causing the clock to gain time.

In some precision clocks there is a smaller auxiliary weight on a threaded shaft to allow more fine adjustment.

However, a heavier bob helps to keep the pendulum moving smoothly until it receives its next push from the clock's escapement mechanism.