A large force acting for a short time to produce a finite change in momentum is called an impulsive force.
Example: (I) Force exerted by a bat, while heating a ball.
(II) Blow of hammer on a nail.
Expression For an Impulse
Let we consider a constant force F which acts on a body for time ∆t. then the impulse is given by
I = F∆t
According to Newton’s second law
F = dp/dt or F.dt = dp
It in time 0 to t, the momentum of the body changes from P₁ to P₂, then
Thus, the impulse of a force is equal to the total change in momentum produced by a force.