Question

Water is flowing continuously from a tap having a bore of internal diameter $8\times {10}^{-3}$m. The diameter of the water stream at a distance $2m$ below the tap is :

(Assume that the velocity of the water as it leaves the tap is $0.4m{s}^{-1}$)

• A. $7\times {10}^{-3}m$
• B. $2\times {10}^{-3}m$
• C. $4.55\times {10}^{-3}m$
• D. $16\times {10}^{-3}m$

Answer 1

The correct option is B $2\times {10}^{-3}m$

Let Velocity of water stream Qm below the tap be V
$V^2=U^2+2as$
$\Rightarrow V^2=(0.4{)}^2+2\times 9.8\times 2$
$\Rightarrow V=6.274m/s$
From Continuity Theorem,
$\pi (4\times {10}^{-3})\times 0.4=6.274\times \pi r^2$
$\Rightarrow r=1.0099\times {10}^{-3}$
So, diameter of the water stream $=2r$
$=2\times 1.0099\times {10}^{-3}$
$=2\times {10}^{-3}m$