Question

Water is flowing continuously from a tap having an internal diameter $8\times {10}^{-3}m$. The water velocity as it leaves the tap is $0.4m{s}^{-1}$. The diameter of the water stream at a distance $2\times {10}^{-1}m$ below the tap is close to:

• A. $9.6\times {10}^{-3}m$
• B. $3.6\times {10}^{-3}m$
• C. $5.0\times {10}^{-3}m$
• D. $7.5\times {10}^{-3}m$

Answer 1

The correct option is B $3.6\times {10}^{-3}m$

$\begin{array}{c}\Delta =8\times {10}^{-3}m\&V=0.4m{s}^{-1}\\ V=\sqrt{u^2+2gh}=\sqrt{{\left(0.4\right)}^2+2\times 10\times 0.2}=2m/s^{-1}\\ A_1{V}_1=A_2{V}_2=\pi \left(\frac{8\times {10}^{-3}}{4}\right)\times 0.4=\pi \times \frac{d^2}{4}\times 2\\ \therefore d=3.6\times {10}^{-3}m\\ Hence,option\left(B\right)iscorrect.\end{array}$