Terminal Velocity Formula — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Terminal Velocity Formula Valid only for small spherical objects moving at low velocities (low Reynolds number) through a viscous fluid where Stokes' Law applies. Assume the object is a sphere falling through a viscous fluid. Identify the forces: Weight (down), Buoyancy (up), and Viscous Drag (up). At terminal velocity, acceleration is zero, so Net Force = 0. Equate Weight = Buoyancy + Drag Force. Substitute formulas: Weight = mg = (4/3)πr 3 ρ s g, Buoyancy = (4/3)πr 3 ρ f g, Drag (Stokes' Law) = 6πηrv. Solve for velocity v. Object must be spherical Flow must be laminar (low Reynolds number) Fluid must be infinite in extent (negligible wall effects) Confusing dynamic viscosity with kinematic viscosity. Applying the formula to turbulent flow or high velocities. Neglecting the buoyant force (density of fluid) when it is significant compared to the sphere's density.