Answer
$v = 1.4~m/s$
Work Step by Step
We can use conservation of energy to find the speed of the block:
$mgh = \frac{1}{2}mv^2+\frac{1}{2}I~\omega^2$
$mgh = \frac{1}{2}mv^2+(\frac{1}{2})(\frac{1}{2}MR^2)~(\frac{v}{R})^2$
$mgh = \frac{1}{2}mv^2+\frac{1}{4}Mv^2$
$mgh = \frac{1}{2}mv^2+\frac{1}{4}(8m)v^2$
$gh = \frac{1}{2}v^2+2v^2$
$gh = \frac{5}{2}v^2$
$v^2 = \frac{2gh}{5}$
$v = \sqrt{\frac{2gh}{5}}$
$v = \sqrt{\frac{(2)(9.8~m/s^2)(0.50~m)}{5}}$
$v = 1.4~m/s$
