Stokes' law

Stokes' law gives the viscous drag on a small sphere moving slowly through a fluid as proportional to the fluid's viscosity, sphere radius, and speed.

Stokes drag: The low-speed viscous drag force on a sphere, equal in magnitude to six pi times viscosity, radius, and speed. This is the force Stokes' law quantifies.
Sedimentation: The settling of suspended particles under gravity or another applied force. Stokes' law predicts the drag opposing a particle's downward motion.
Newton's drag equation: A model in which drag on an object is proportional to fluid density, squared speed, and frontal area. It describes inertial drag at higher speeds, unlike Stokes' linear-speed relation.
George Gabriel Stokes: An Irish mathematician and physicist whose work shaped fluid mechanics, optics, and mathematical physics. He derived the low-speed sphere-drag relation in his study of viscous fluids.
Reynolds number: A dimensionless ratio comparing inertial effects with viscous effects in fluid flow. A very small value marks the regime where Stokes' law is reliable.
Terminal velocity: The constant speed reached when an object's net force becomes zero. A falling sphere reaches this speed when Stokes drag balances its effective weight.
Oseen approximation: A correction to creeping-flow theory that retains leading effects of fluid inertia. It improves on Stokes' law when Reynolds number is small but not negligible.
Viscosity: A fluid property describing resistance to relative motion between neighboring layers. Stokes' law expresses how viscosity produces drag on a moving sphere.
Navier–Stokes equations: Partial differential equations governing the motion of viscous fluids. Stokes' law follows from their creeping-flow limit around a sphere.
Millikan oil-drop experiment: An experiment that measured the elementary electric charge by balancing forces on charged oil droplets. Stokes' law helped infer droplet sizes and viscous drag.

Linked from 19 pages