## Essential University Physics: Volume 1 (4th Edition)

$32\ MJ$
We first find the inertia: $I = \frac{1}{2}MR^2 = \frac{1}{2} \times 135 \times (.3)^2 = 6.1\ kgm^2$ Next, we convert rotations per minute to radians per second. This gives that the object is rotating at $3246 \ rads/s$. Thus, we find: $K_{rotational}= \frac{1}{2}I\omega ^2 = \frac{1}{2}(6.1)(3246)^2= 32\ MJ$