DEFINITION

Linear momentum is the quantity given by the product of mass and velocity of a body, p = m v .Momentum is a vector quantity as it is the product of a scaler (mass) and a vector (velocity)

From newtons 2nd law, F = m a, substituing a = (v_final - v_initial) / _t we see that F = ( mv_final - mv_initial) / _t, or as m is a constant, force is equal to rate of change of momentum ^dp/_dt.