Momentum [kg-m/s] 1 ? 0.1 0.2 0.3 0.4 0.5 Time [s] Figure 1.21: Momentum as a function of time[1] 22 object is not "in equilibrium," meaning that this time the net force on the object is not zero. Net force is given by Newton's Second Law: Fnet = Ap At Py, f "A" means "change in... so Ap = p p, final momentum, with subscript f, minus initial momen- tum, with subscript i. (1.7) = Rearranging, Ap Fnet At. The momentum changes linearly from zero to its final value... = -7.84 N 0.5 s = -3.92 kg-m/s .