Q. Blood is flowing at the rate of $200\ cm^{3}\ s^{- 1}$ in a capillary of cross sectional area $0.5\ m^{2}$. The velocity of flow, in $mms^{- 1}$, is
A) 0.1
B) 0.2
C) 0.3
D) 0.4
Explanation
(d) Given $A = 0.5 \times 10^{6}mm^{2};V = 200 \times 10^{3}mm^{3}$
$\frac{dV}{dt} = \frac{d(Al)}{dt} = A\frac{dl}{dt} = Av$
$v = \frac{1}{A}\left( \frac{dV}{dt} \right) = \frac{1}{0.5 \times 10^{6}}\left( 200 \times 10^{3} \right) \Rightarrow v = 0.4\ mms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.