A 1.5kg block and a 2.7kg block are attached to opposite ends of a light rope.The rope hangs over a solid, frictionless pulley that is 33 cm diameter and has a mass of 0.72kg.When the blocks are released, what is the acceleration of the lighter block?

Since there's no friction then the Pulley will not rotate as the torques due to tension cancels out.Using Newton's Second law,

Mg - T = Ma and T -mg = ma, T is the tension here, M is mass of heavier block and m of the lighter block.Eliminating T from the above equations

Mg - mg = (M+m)a where g is acceleration due to gravity=> a = (2.7g - 1.5g) / 4.2

The quantity a is the acceleration of both the blocks forming the system.