In classical mechanics, an impulse's defined as the integral of a force with respect to time. When a force's applied to a rigid body it changes the momentum of that body. A small force applied for a long time can produce the same momentum change as a large force applied briefly, because it's the product of the force and the time for which it's applied that's important. Mathematical derivation » mathbfDelta t = mv_1 - mv_0 where » F's the constant total net force applied, t's the time interval ov… (More on Impulse)