A mass of 7.1 kg is attached to the free end of a light string wrapped around a pulley (the pulley is a disk) of radius of 1.36 m and mass 6 kg. The pulley is free to rotated in a vertical plane about the horizontal axis passing through its center. The weight is released 8.2 m above the floor. Find the speed of the mass when it hits the ground by using the conservation of energy.