Anybody know the physics of tube/pipes under water?

Question

You see it in films, but does it work? Is it possible to sit on a river bed and hide from the baddies with a tube and breathe air? Is there a depth when this is impossible?

Answer 1

Experienced divers have no trouble diving 15-20 feet deep without assistance. With two tubes, one for inhaling and one for exhaling, you could do it indefinitely. One tube is enough if you don't care about people seeing bubbles, or if you have someplace else to put the exhaled air.

Answer 2

There is a limit to how deep and it isn't very deep at all. Water generates a pressure of 0.43 psi per foot of depth. When you breath, your chest must expand against this pressure. Typically, your chest has a surface area of a couple hundred square inches (say 10 inches by 10 inches front and back). The total force needed to expand your chest os the product of pressure and area. At 1 foot depth, this is 86 pounds (really more because the 10x10 is small) . At less than 2 feet of depth it becomes nearly impossible to breathe.

You can try this for yourself, but in reverse. Take a glass of water and a piece of clear plastic tubing (hardware stories carry tubing) about 4 feet long for a straw. Put the glass on the floor, stand up and try to drink through the straw. You will find that you can only raise the water level in the sraw 1-2 feet. The differential pressure is the same as trying to breathe underwater and the height of the water is the same as the depth you could breathe at.

Answer 3

With your lungs doing the pumping and if the hose is very long it want work. with the watter pressure it is hard to change that Much air. The second problem is inhaling in the same tube as u exhale u will soon become unconscious,due to the re-breathing of the CO2.

Answer 4

I tried it when i was a lad and the most I could do was when my chest was about two feet under water so the top of my head was only a few inches under I never tried it lying down but i suppose the same depth would apply.

Answer 5

Completely possible - so long as the air volume of the tube is a lot less than your lung capacity!!

Answer 6

About a metre - they say as you have the problem of expelling the dead air, as well as pushing against water pressure.

Answer 7

hollywood has a 'creative limit', you can breath in water as long as you like, (it contains oxygen) you just have to have total control over your fear of drowning, i have trired it, i lasted 21 mins, it is all in the head, as is life

Answer 8

go