$1\mathrm{.}6\mathrm{.}26$ A $0\mathrm{.}3$ m $-$diameter circular plate is placed over a fixed bottom

plate with a $0\mathrm{.}0025$ m gap between the two plates filled with glycerin,

as shown in Fig. P$1\mathrm{.}6\mathrm{.}26.$ Determine the torque required to rotate the

circular plate slowly at $2$ rpm $.$ Assume that the velocity distribution in

the gap is linear and that the shear stress on the edge of the rotating

plate is negligible.

FIGURE P$1\mathrm{.}6\mathrm{.}26$