Q. The velocity of a small ball of mass M and density $d_{1}$ when dropped in a container filled with glycerine becomes constant after some time. If the density of glycerine is $d_{2}$, the viscous force acting on the ball is
A) $Mg\left( 1\frac{d_{2}}{d_{1}} \right)$
B) $Mg\frac{d_{1}}{d_{2}}$
C) $Mg(d_{1} - d_{2})$
D) $Mgd_{1}d_{2}$
Explanation
(a) Viscous force upwards = Apparent weight in liquid
$\therefore\ Viscous\ force = Mg - \frac{Mgd_{2}}{d_{1}}$
$Viscous\ force = Mg\left( 1 - \frac{d_{2}}{d_{1}} \right)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.