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A horizontal tube has a T-junction with a vertical tube coming downwards into a container of liquid, at height h below the T-junction. Air is forced into the horizontal tube which causes a pressure difference which sucks the liquid up the vertical tube.

What is the pressure at the top of the vertical tube?

I have the answer as

P = Po - 1/2 * /rhoA * v^2

where:

P = pressure at top of vertical tube

Po = atmospheric pressure

/rhoA = density of air in tube

v = velocity of air in tube

but I can't seem to derive this equation from Bernoulli's equation. (Or anything else! )

Any ideas?

Thanks.

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# Bernoulli's equation - finding the pressure at the top of a tube

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