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A pressure-pump has a horizontal tube of cross sectional area 10 \mathrm{~cm}^{2} for the outflow of water at a speed of 20 \mathrm{~m} / \mathrm{s}. The force exerted on the vertical wall just in front of the tube which stops water horizontally flowing out of the tube, is :
[given: density of water =1000 \mathrm{~kg} / \mathrm{m}^{3} ]
 

Option: 1

300 \mathrm{~N}


Option: 2

500 \mathrm{~N}


Option: 3

250 \mathrm{~N}


Option: 4

400 \mathrm{~N}


Answers (1)

best_answer

\mathrm{A=10 \mathrm{~cm}^2=10 \times 10^{-4 \mathrm{~m}^2}}

\mathrm{V=20 \mathrm{~m} / \mathrm{s}}

\mathrm{\Delta p_{\text {wall }}-\Delta P_{\text {wall }}=P_i-P_f}

\mathrm{\Delta p=(\Delta m)v-0}

\mathrm{\Delta p=(\Delta m) v }

\mathrm{\Delta p_{\text {wall }}=\rho(A \Delta x) v}
Force exerted on wall is

\mathrm{F=\frac{\Delta P \text { wall }}{\Delta t}=\rho A \frac{(\Delta x)v}{\Delta t}}

\mathrm{F=\rho A V^2}

    \mathrm{=10^3 \times 10^{-3} \times(20)^2}
\mathrm{F=400 \mathrm{~N}}

Hence 4 is correct option.



 

Posted by

Divya Prakash Singh

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