I have corrected my previous posting where I inadvertently dropped m on the LHS of the eq in the last two steps.You can alternatively solve it by following way-

mg*2sin30 = (1/2)Iw^2 + (1/2)mv^2

mg = (1/2)(mr^2/2)w^2 + (1/2) m r^2w^2, cancel m both the side and get

g = (3/4)r^2w^2