A 12-in.-diameter circular plate is placed over a fixed bottom plate with a -in. gap between the two plates filled with glycerin as shown in Fig. P1.89. Determine the torque required to rotate the circular plate slowly at \(2 \mathrm{rpm}\). 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 P1.89

Rotating plate Torque 0.1-in. gap.