An object descends from a pulley. http://img501.imageshack.us/img501/9783/physics12qm.th.jpg [Broken] Use the conservation of mechanical energy to find the linear speed of the descending mass (m = 1.0kg) after it has descended a vertical distance of 2.0m from rest. (For the pulley, M = 0.30kg and R = 0.15m. Neglect friction and mass of the string) I solved this question not using the conservation of mechanical energy. At first I tried using it though and I wound up getting: vcm = square root of (4/3 mgh/M) However, I determined the acceleration using a pervious example: a = 2mg/(2m + M) and then used v2 = 2ax and got 5.8m/s which is the right answer... but I don't know how to solve this question using the conservation of mechanical energy.