Consider a body of mass m, initial velocity of magnitude u, a force F acts on the body to a final velocity of magnitude v. We have from Newton's second law F= m(v-u)/t or F = (mv-mu)/t. mu is the initial momentum of the body and mv is the final momentum of the body.

Force = rate of change of momentum.

F = DP/Dt or Dp = F x Dt

The FDt is called the impulse of the force F.

The change in momentum can be calculated by the area under the graph of force against time.

F = D (mv)/Dt

= m/Dt x Dv.