On Moon: It would take the same ammount of time to get down as it took to go up(maximum displacement, when v = 0). Thus, V(t) = ds/dt = 832 - 5.2t = 0. t = 160s. It would take about 2 minutes and 40 seconds. On Earth: Same notion. V(t) = ds/dt = 832 - 32t = 0. t = 26s. -- Am I right? Because V(t) = ds/dt = 3t^2 - 12t + 9, a(t) = dv/dt = 6t - 12 Particle has v = 0 at t = 3, and 1 sec Thus, the particle has acelleration at v = 0 at: a(3) = 6 m/s^2 and a(1) = -6 m/s^2 -- Am I right? Please correct my mistake. Thanks.