High Quality Content by WIKIPEDIA articles! In 1851, George Gabriel Stokes derived an expression, now known as Stokes` law, for the frictional force – also called drag force – exerted on spherical objects with very small Reynolds numbers (e.g., very small particles) in a continuous viscous fluid. Stokes` law is derived by solving the Stokes flow limit for small Reynolds numbers of the generally unsolvable Navier–Stokes equations: