Stokes Law — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Stokes' Law Valid only for small spherical objects moving at low velocities (laminar flow) through a homogeneous, infinite fluid medium where the Reynolds number is very small. Dimensional analysis (Buckingham Pi theorem) indicates dependence on viscosity, radius, and velocity. Exact coefficient 6π is derived from solving the Navier-Stokes equations for creeping flow around a sphere. Assumes inertial forces are negligible compared to viscous forces. Object must be spherical Fluid must be of infinite extent compared to the object size (no wall effects) Flow must be laminar (low Reynolds number) No slip condition at the fluid-solid interface Believing it applies to objects of any shape (it is specific to spheres). Applying it to turbulent flow situations (high velocity). Confusing dynamic viscosity with kinematic viscosity.