Though the theory of viscosity has a number of applications, yet the viscous resistance on bearings is important. The following points may be noted for viscous resistance:

(a) Torque required to overcome viscous resistance of footstep bearing is:

N = Speed of the shaft,

R = Radius of the shaft, and

t = Thickness of the oil film.

(b) Torque required to overcome viscous resistance of a collar bearing is

where

R1 and R2 = External and internal radius of collar.

(c) The coefficient of viscosity may be found out, experimentally, by the following methods:

(i) Capillary tube method

(ii) Orifice type viscometer;

(iii) Rotating cylinder method; and

(iv) Falling sphere method.

(d) The coefficient of viscosity (in poises), according to the method of orifice type viscometer, is