Q. Two different liquids are flowing in two tubes of equal radius. The ratio of coefficients of viscosity of liquids is 52:49 and the ratio of their densities is 13:1. then the ratio of their critical velocities will be
A) 4 : 49
B) 49 : 4
C) 2 : 7
D) 7 : 2
Explanation
(a) Critical velocity $v = N_{R}\frac{\eta}{\rho r}$
$\Rightarrow \frac{v_{1}}{v_{2}} = \frac{\eta_{1}}{\eta_{2}} \times \frac{\rho_{2}}{\rho_{1}} = \frac{52}{49} \times \frac{1}{13} = \frac{4}{49}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.