1. The problem statement, all variables and given/known data A ball of mass 0.150 kg is dropped from rest from a height of 1.25 m. It rebounds from the floor to reach a height of 0.960 m. What impulse was given to the ball by the floor? 2. Relevant equations Δmv/t =I vf^2=vo^2 +2aΔy 3. The attempt at a solution mghi = mghf +1/2mvf^2 vf = 2.38m/s 0.150kg x (2.38-0) = 0.35 Kg m/s But this did not work. What the answer key did was use kinematics equations to find the velocity before the ball hit the ground and then found the velocity when the ball reached the height 0.960m. They then did change in velocity x mass to find the impulse. Essentially, I don't see why using the conservation of energy equation to find the change in velocity is wrong. Why does this not work?