State Stokes' law and define terminal velocity.

Stokes' law states that the viscous force on a small sphere of radius r moving with velocity v through a fluid of coefficient of viscosity η is F = 6πηrv. Terminal velocity is the constant velocity a body reaches when the viscous force and the upthrust together balance its weight, so the net force and the acceleration become zero.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

A raindrop reaches its terminal velocity within a few metres of falling.