Consider the apparatus shown below. The space between the disk and the solid boundary is

$1\mathrm{.}60$ mm and is filled with oil with viscosity of $0\mathrm{.}039N.\frac{s}{m^2}.$ The radius of the disk is $9$ cm $.$

The disk is rotated at $22ra\frac{d}{s}.$ Find the shear stress at $r=1\mathrm{.}5cm$ and $r=3\mathrm{.}5cm,$ where $r$ is

the radial distance from the center of the disc. Also, find the torque required to rotate the disk

$($see hint below for solving the problem$).[15]$

Oil