Easy# Torque and Equilibrium

APPHMC-XWEEF6

The solid cylinder depicted above with moment of Inertia, $I$, is being acted on by force, $F$, that acts tangentially along the edge of the disc as depicted above.

What must be the value of force *$F^\prime$* so that the cylinder rotates at a constant angular velocity if $r=\frac{R}{2}$.