Question

The mass of water flowing in $10$ minutes through a tube $0.1cm$ in diameter, $40cm$ long if there is a constant pressure head of $20cm$ of water is: ($\eta$ for water $=0.008$ C.G.S units and $g=1000cm{s}^{-2}$)

• A. $19.3\pi gm$
• B. $\left(29.3\right)\pi gm$
• C. $49.3\pi gm$
• D. $59.3\pi gm$

Answer 1

The correct option is B $\left(29.3\right)\pi gm$

The flow rate per unit time from the pipe $=\frac{\pi \left(Pg20\right)(0.005{)}^4}{8\times 0.008\times 40}$

$=\pi \left(0.04882653\right)c{m}^3/s$

So, mass of water flowing in $10$ minutes
$=\pi \left(0.048820\right)\times 10\times 60\times 1g/cc$
$=\left(29.29\pi \right)gm$
$=29.3\pi gm$