1. The problem statement, all variables and given/known data The two masses(m1 = 5.0 kg and m2 = 3.0 kg) in the Atwood's machine shown below are released from rest, with m1 at a height of 0.75 m above the floor. When m1 hits the ground its speed is 1.8 m/s. Assuming that the pulley is a uniform disk with a radius of 12 cm, determine the pulley's mass. http://img23.imageshack.us/img23/904/pulleyl.jpg [Broken][/URL] 2. Relevant equations Rotational kinematics 3. The attempt at a solution I don't really know where to start here. Could someone please start me off?