Q. $16\ cm^{3}$ Of water flows per sec through a capillary tube of radius $a$ cm and of length $l$ cm when connected to a pressure head of $h$ cm of water. If a tube of the same length and radius $a/2$ cm is connected to the same pressure head, the quantity of water flowing through the tube per second will be
A) $16\ cm^{3}$
B) $1\ cm^{3}$
C) $4\ cm^{3}$
D) $8\ cm^{3}$
Explanation
(b) $V = \frac{\pi\ p\ r^{4}}{8\ \eta\ l},\ ie,\ V \propto r^{4}$
$\frac{V^{'}}{V} = \frac{(a/2)^{4}}{a^{4}} = \frac{1}{16}$ or $V^{'} = \frac{V}{16} = \frac{16}{16} = 1\ cm^{3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.