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Consider a siphon tube... Now consider the opening of the tube at the lower end. Isn't the pressure at the mouth of the tube, at this lower end, something intermediate between $P_a$ and $P_a + \rho gh$? ($h$ represents the difference in the height of the water surfaces in the two containers used). To ensure the flow of liquid in both the tube and the container in which it is dipped, shouldn't this be the case? Because if it is equal to $P_a$, then the liquid in the container will not move and keep balance. If it is $P_a + \rho gh$, then the liquid in the tube will not move. So shouldn't it be something intermediate? But the book says that the pressure at this end is $P_a$. Is the book approximating the value?

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  • $\begingroup$ can you supply a picture of the siphon you mean? But the pressure at any open end ist the pressure of the medium outside the opening. $\endgroup$
    – trula
    Commented Jul 27, 2020 at 13:44
  • $\begingroup$ I tried but couldn't upload the image... Is there any other way? $\endgroup$
    – user266637
    Commented Jul 27, 2020 at 13:53

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The flow of liquid in a siphon tube is not caused by a pressure difference between the ends. It is caused by the unsupported weight of the fluid in the tube which lies below the level of the liquid in the source.

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  • $\begingroup$ I added a picture, you can throw it away an ad you own one, by editing your post (not in a comment) maybe your picture was too large? Does my picture apply to your question? $\endgroup$
    – trula
    Commented Jul 27, 2020 at 14:11
  • $\begingroup$ I can't see the picture... $\endgroup$
    – user266637
    Commented Jul 27, 2020 at 14:14

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