Strokes law is an expression derived by George Gabriel Stokes. It is derived from the frictional force, also known as drag force that is applied on spherical objects possessing very small Reynolds numbers in a viscous fluid. This law is applied in several areas of the science. Use our online calculator to find the frictional force that is acting on the interface between the fluid and the particle. Enter the radius, shear viscosity and velocity to get the frictional force.