1. The problem statement, all variables and given/known data The two masses (m1 = 5.2 kg and m2 = 2.6 kg) in the Atwood's machine shown in The Figure are released from rest, with m1 at a height of 0.79 m above the floor. When m1 hits the ground its speed is 1.7 m/s. Assuming that the pulley is a uniform disk with a radius of 12 cm, outline a strategy that allows you to find the mass of the pulley. Determine the pulley's mass. 2. Relevant equations Rotational Kinetic Energy: K + (1/2)Iw2 Conservation of Energy: Ki + Ui = Kf + Uf 3. The attempt at a solution I am more or less stumped on this problem. Information that is known is that v0 = 1.7 m/s and vf = 0. The Ei = mgh (I think since the system starts at rest and m1 has Gravitation Potential Energy). Ef = (1/2)mv2 + (1/2)Iw2. All this is speculation since I am grasping at a way to solve this problem. Also, from looking at other related problems people tend to find acceleration through the Kinematics v2 - v02/2(x - x0). However, I am not sure how to apply the acceleration of m1, all I know is that it translates through the pulley system. Another possible acceleration I found was a = [(m1 - m2)/(m1 + m2)]g. This formula brought up a different acceleration than the previous, but once again I am not certain how to apply it. Reassurance that I am on the right route, and a hint would be greatly appreciated.