Which of the following diagrams correctly shows the relation between the terminal velocity VT of a spherical body falling in a liquid and viscosity v of the liquid?

Answer: (c)

The force of viscosity acting on a smooth sphere in stream line motion can be expressed with Stock's formula -

F = 6 πηrv

Where F = force (N)

η = viscosity of fluid

r = radius of sphere (m)

v = relative velocity between fluid and sphere (m/s) or terminal velocity.

∴ v ∝ 1/η

Velocity decreases for each terminal velocity.