A cord is wound round the circumference of wheel of radius $r$, The axis of the wheel is horizontal and the moment of inertia about it is $I$. A weight $m g$ is attached to the cord at the end. The weight falls from rest. After falling through a distance h , the square of angular velocity of wheel will be\\
(1) $\frac { 2 m g h } { I + m r ^ { 2 } }$\\
(2) $\frac { 2 m g h } { I + 2 m r ^ { 2 } }$\\
(3) $2 g h$\\
(4) $\frac { 2 g h } { I + m r ^ { 2 } }$