Question

A solid ball of volume V is dropped in a viscous liquid. It experiences a viscous force F. If the solid ball of volume $2V$ of same material is dropped in the same fluid, then the viscous force acting on it will be

• A. $nF/2$
• B. $F/2$
• C. $2F$
• D. $2nF$

Answer 1

The correct option is C $2F$

Viscous force, $F=6\pi \eta rv$
but $v\propto r^2$
$\therefore F\propto V$ (volume)
So, on doubling the volume of the ball, the viscous force is doubled.