Answer
$F=3.43 \times 10^{-4} \mathrm{lb}$
Work Step by Step
$\begin{gathered}\tau=\mu \frac{d u}{d y}=\mu \frac{U}{b} \\ U=\omega R=10,000\left(\frac{1}{60}\right)(2 \pi)\left(\frac{2}{12}\right)=175 \frac{\mathrm{ft}}{\mathrm{s}} \\ \tau=\left(3.74 \times 10^{-7}\right) \frac{175}{\left(\frac{0.005}{12}\right)}=1.57 \frac{\mathrm{lb}}{\mathrm{ft}^2} \\ F=\tau A=(1.57) \frac{\pi}{4}\left(\frac{0.2}{12} \mathrm{ft}\right)^2=3.43 \times 10^{-4} \mathrm{lb}\end{gathered}$
