1. The problem statement, all variables and given/known data The impulse on a human cannon ball is 2.5 103 N·s. The cannon ball has a mass of 65 kg. 2. Relevant equations How long is the barrel of the cannon if the cannon ball leaves the cannon at 120 km/h? 3. The attempt at a solution I used the formula J=ma(delta t) (2.5x 10^3)=(65)(a)(0.2) to find the acceleration. Then, I used the formula d=v1(t)+(1/2)(a)(t^2) to find the distance, and I got 3.85 m, but the answer at the back is wrong. Can anybody help me?