energy is conserved, no slipping or air resistance or anything. There is a pulley, on one side is a mass resting on the ground, and on the other side is a larger mass above the ground. If the larger mass is released, what is it's speed when it hits. okay, here is what I have: PgM = Pgm + KM + KR + Km Mgh = mgh + v[ srqt(.5M) + sqrt(.5I)/r + sqrt(.5m) ] I= .5mr^2 = .5(7.50kg)(.260m)^2 = 0.2535kg*m^2 h=3 m=18 M=26.5 so PgM = 779.1 J Pgm = 529.2 J My answer is v(M)=49.84m/s, completely illogical, and the book answer is 3.22m/s. What did I do wrong? All the numbers look right, and it appears to make sense, but the answer is way off... Thanks for any help!