球形物体在流体中运动所受到的阻力，等于该球形物体的半径、速度、流体的黏度与6π的乘积。这个定律叫做斯托克斯定律。

如果物体在流体中因自身的重量而下落，则其最终速度为：

In 1851, George Gabriel Stokes derived an expression, now known as Stokes' law, for the frictional force – also called drag force – exerted on sphere/spherical objects with very small Reynolds numbers (i.e. very small particles) in a viscous fluid. Stokes' law is derived by solving the Stokes flow limit for small Reynolds numbers of the Navier–Stokes equations: