1. The problem statement, all variables and given/known data Two people are standing on a 2.3 m long platform, one at each end. The platform floats parallel to the ground on a cushion of air, like a hovercraft. One person throws a 6.9 kg ball to the other, who catches it. The ball travels nearly horizontally. Excluding the ball, the total mass of the platform and people is 128 kg. Because of the throw, this 128 kg mass recoils. How far does it move before coming to rest again? 2. Relevant equations 3. The attempt at a solution i tried the problem by drawing a diagram i got 0.12m but that answer's not right, and i have no clue why!!