Answer
0.8 Nm
Work Step by Step
Torque is found from $\tau=I\alpha$. Angular acceleration can be found from $\omega=\omega_0+\alpha t$. Initial angular velocity is 0. The rotational inertia is that of a cylinder.
$$\tau=I\alpha=\frac{1}{2}MR^2(\frac{\omega-\omega_0}{t})=(0.5)(1.6kg)(0.2m)^2\frac{(24\frac{rev}{s})(2 \pi \frac{rad}{rev})}{6s}=0.8Nm$$
