Question

A bucket of oil is released at the top of a building to hit a person. The mass of the bucket with the oil is 2.5kg and it is attached to a massless string that is wrapped around a cylindrical drum. As the bucket falls, the drum rotates and you may assume that there is no slippage. If the drum has a radius of .85m and a mass of 12.5kg,what is the angular speed of the drum after the oil has fallen a distance of 4.5m? Use the conservation of energy.