Here's my problem:- 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.