"By means of a rope, whose mass is negligible, two blocks (mass: 11kg and 44 kg) are suspended over a pulley. The pulley can be treated as a uniform solid cylindrical disk. The downward acceleration of the 44 kg block is observed to be exactly one half the acceleration due to gravity. Noting that the tension in the rope is not the same on each side of the pulley, find the mass of the pulley."
The answer of 22 kilograms is in the back of the book, but I need someone to point me in the right direction as to the steps I need to take to arrive at this solution.