Stokes' Law describes the force of viscosity on a small sphere moving through a viscous fluid. The law is named after the British scientist George Gabriel Stokes, who derived the formula in 1851. Stokes' Law is given by:
F = 6πηrv
where F is the drag force, η is the dynamic viscosity of the fluid, r is the radius of the sphere, and v is the velocity of the sphere relative to the fluid.