Answer
(a) $0.068~m\cdot N$
(b) Because of the friction from the potter's hands, the wheel would stop in 16 seconds.
Work Step by Step
(a) $\tau = r\cdot F = (0.045~m)(1.5~N) = 0.068~m\cdot N$
(b) We can find the magnitude of angular deceleration if the only torque is from friction.
$I\alpha = \tau$
$\alpha = \frac{\tau}{I} = \frac{0.068~m\cdot N}{0.11~kg\cdot m^2}$
$\alpha = 0.618~rad/s^2$
We can use $\alpha$ to find the time to stop:
$t = \frac{\Delta \omega}{\alpha} = \frac{0-(1.6~rev/s)(2\pi~rad/rev)}{-0.618~rad/s^2}$
$t = 16~s$
Because of the friction from the potter's hands, the wheel would stop in 16 seconds.