* Stokes’ law*, which was derived in 1851 by an Irish scientist named George Stokes, describes the drag force exerted on a spherical object in a viscous fluid through the formula:

where

*F*_{d }is the frictional force (drag) acting on the surface of the object

*μ* is the viscosity of the fluid

*r* is the radius of the spherical object

*u* is the flow velocity of the fluid

The derivation of the equation for Stokes’ law involves the following steps:

Step 1: Derive the continuity equation in spherical coordinates for an incompressible fluid.

Step 2: Define the Stokes stream function to satisfy the continuity equation for an incompressible fluid.

Step 3: Derive the Navier-Stokes equations.

Step 4: Derive the differential equation, *E ^{2}*(

*E*) =

^{2}ψ*0*.

Step 5: Solve the differential equation.

Step 6: Derive the Stokes’ law equation.