Could someone help me out with this one, I cant seem to get on track here. A ball of mass 3.5 kg is thrown upward. It leaves the thrower's hand with a velocity of 12 m/s. The ball is in the air for 2.4 seconds. Final velocity before the ball returns to the hand in -12 m/s. The change in momentum in the ball is -84 N*s. The implus calculated from the change in momentum is -84 N*s. How would I calculate the average force acting on the ball? I though it should be -84/2.4 (change in momentum/change in time). -35 however is not correct.