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Suppose I have a ten foot tube with one of the ends sealed air tight. The tube is lifted vertically with the open end of the tube under the water surface. Some of the air inside of the tube is removed to raise the level of the water to about two feet. What is the pressure of the remaining air inside of the tube? Thanks! I promise to choose a best answer!
Are you guys sure that the pressure will be reduced? That is what I originally thought, but now am beginning to wondering if the water that flows into the tube helps to maintain the pressure.
3 Answers
- ?Lv 77 years agoFavorite Answer
The pressure inside is dependent on how far down you have the tube. Just like a diver, the further you go down, the higher the pressure. You didnt say the top was at the surface.
As stated, water pressure =0.433 PSI per foot of depth.
The tube also needs pressure to hold back the water.
Depending on the depth and the pressure, subtract 2*0.433 (for the removed 2 feet of water)
That will be the pressure in the tube.
Source(s): M. Engineer - az_lenderLv 77 years ago
Pressure at the bottom of the tube will be the same both inside and outside the tube, so the pressure at sea-level will be the same both inside and outside the tube. If it's 14.696 psia outside the tube, then the 14.696 psi is the sum of (a) the air pressure inside the tube and (b) the pressure exerted by two feet of water. One ft^3 of water weighs 62.4 lb, and at its base exerts a pressure of 62.4 lb/(144 in^2) = 0.43333 psi, so a column of 2 feet of water exerts a pressure of 0.8667 psi, and the air pressure inside the tube must be 14.696 psi - 0.867 psi = 13.83 psi. Could range from 13.5 to 14.1 depending on weather conditions.
- Ray;mondLv 77 years ago
Sea level air pressure = 14.7 pounds per square inch (average) will lift a column of fresh water about 39 feet, so two feet is 14.7 divide by 19.5 = 0.7538 pounds per square inch less than the ambient air pressure = about 14 psi if the barometer is low or you live a few hundred feet above sea level
