A doubt about pressure

  • #1
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Hi, I wonder if what I think is in according to the theory in Why the liquid falls. Check out the image I've uploaded. (sorry my bad english)
 

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  • #2
pbuk
Science Advisor
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No, this is nothing to do with atmospheric pressure (the same thing will happen in a vacuum) and the liquid will continue to flow until the surface in each container is at the same level (ie the depth in the lower container is greater).
 
  • #3
DaveC426913
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The reason liquid flows in a siphon is because the weight of the water in the left side of the hose outweighs the water in the right side.

Imagine, instead of water, you had a long piece of string in the hose. At the right end of the string there is one marble tied to the string, at the left end, there are TWO marbles tied, weighing twice as much. Discounting friction, the string and marbles will slide into the lower bucket.
 
  • #4
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yes, I know that. But why it happens? Is it not because the difference between the pressure in each container?
 
  • #5
DaveC426913
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Is it not because the difference between the pressure in each container?
No. Either side (or both) could be a 5 gal pail or an ocean. It would make zero difference.

What would make a difference is the height. A siphon falling 50 feet will be very powerful. A siphon falling 6 inches will be very weak, because there's very little pressure differential. That's also why - when the water level on both sides is equal - the siphoning process stops completely.

yes, I know that. But why it happens?
?? It happens because of the weight of water in the pipe.
 
  • #6
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good DaveC. I was typing my comment when you did your post. (sorry my bad english). Thank you.
 

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