**(i) Impulsive Force**

An impulsive force is a very great force acting for a very short time on a body, so that the change in the position of the body during the time the force acts on it may be neglected.

Example: The blow of a hammer, the collision of two billiard balls etc.

**(ii) Impulse of a force**

The impulse J of a constant force F acting for a time t is defined as the product of the force and time.

**Impulse = Force x time **

**Or, J = F x t **

The impulse of force F acting over a time interval t is defined by the integral.

**J = ^{t}∫_{o}F dt**

The impulse of a force, therefore can be visualized as the area under the force versus time graph as shown in Figure. When a variable force acting for a short interval of time, then the impulse can be measured as,

**J = F _{average} x dt**

Impulse of force is a vector quantity and its units is N s.