**4 (Solved example in the book - 7th edition)A oil film of viscosity u and thickness lies between a solid wall and a circular disk, h << R as in Fig. E1.10. The disk is rotated steadily at angular velocity 2. Noting that both velocity and shear stress vary with radius r, derive a formula for the torque M required to rotate the disk.Neglect air drag.

Fig: 1

Fig: 2