Question

Water flow through a horizontal pipe of varying cross section at the rate of 50 litres per minute then what will be the velocity of water at a point where diameter is $10 cm ?$

• A. $0.301 ms ^{-1}$
• B. $0.629 ms ^{-1}$
• C. $0.0424 ms ^{-1}$
• D. $0.112 ms ^{-1}$

Answer 1

Answer: (C)

Volume of the water flowing per second.
$V =\frac{20}{60}=\frac{1}{3} \times 10^{-3} m ^{3} s ^{-1} \,\,\left(\begin{array}{l}1 m ^{3}=1000 L \\ 1 L =10^{-3} m \end{array}\right)$
(a) Area $=\pi r^{2}$
$=3.14 \times\left(\frac{10}{2} \times 10^{-2}\right)^{2}$
$=3.14 \times 25 \times 10^{-4}$

$v =\frac{10^{-3} \times 10^{4}}{3 \times 78.5}$
$=\frac{10}{235.5}=0.0424 m / s$