Question

At what speed, the velocity head of a stream of water be equal to $40\text{cm of Hg?}$

• A. $1032.6{\text{cms}}^{-1}$
• B. $432.6{\text{cms}}^{-1}$
• C. $632.6{cms}^{-1}$
• D. $832.6{\text{cms}}^{-1}$

Answer 1

Answer: (A)

$1032.6{\text{cms}}^{-1}$

$40\text{cm of Hg}=\frac{40\times 13600}{1000}\text{cm of water}=544\text{cm of water and velocity head}=\frac{v^2}{2g}$
$\Rightarrow 544=\frac{v^2}{2\times 980}\because g=980cm/s^2\Rightarrow v^2=544\times 2\times 980\Rightarrow v=1032.6{\text{cms}}^{-1}$