Question

A syphon is used at point A to draw the water from large reservoir and discharge it to the point B at an atmospheric pressure. If the elevation difference of points A and B is 10 m, what is the velocity (m/s) at point B?

• A. 10
• B. 14
• C. 24
• D. 34

Answer 1

The correct option is B 14


Applying Bernoulli's equation between A and B, assuming there is no loss due to friction or any minor losses.

$\frac{P_{\text{atm}}}{\rho g}+\frac{V_A^2}{2g}+Z_A=\frac{P_{\text{atm}}}{\rho g}+\frac{V_B^2}{2g}+Z_B$

$\text{Velocity at A,}{V}_A=0$

$\frac{V_B^2}{2g}=Z_A-Z_B=10m$

$V_B^2=10\times 2\times 9.81$

$V_B=\sqrt{10\times 2\times 9.81}$

$V_B=14\text{m/s}$

Note:
Syphon is a long bent pipe which is used to transfer liquid from a reservoir at a higher elevation to another reservoir at a lower level when the two reservoirs are separated by a hill or high level ground.