Centre of Percussion

The centre of oscilation is sometimes termed as centre of percussion. It is defined as that point at which a blow may be struck on a suspended body so that the reaction at the support is zero.

Consider the case of a compound pendulum suspended at O as shown in fig. Suppose the pendulum is at rest in the vertical position, and a blow is struck at a distance L from the centre of suspension. Let the magnitude of blow is F newtons. A little consideration will show that this blow will have the following two effects on the body:

1. A force (F) acting at C will produce a linear motion with an acceleration a, such that

F = m.a

where m is the mass of body.

2. A couple with moment equal of F x l which will tend to produce a motion of rotation in the clockwise direction about the centre of gravity G.