POP QUIZ: How deep do you gotta be....

[TexasMike]

My DiveMaster instructor sprung this question on our class during the "physics of diving" review and I thought it would be a good one for our little gang.

• You have a SCUBA cylinder charged to 3000psi. How deep do you have to be such that when you opened the valve, nothing happens?

Extra credit if you show your math work so the new divers can understand.

 

[chris_b]

Well, let's see I'm a newbie so this should be a good exercise...

3000psi is about 200 atmospheres, and for each 10 meters below sea level, the pressure increases 1 atmosphere. So at 2 kilometers underwater, the pressure of the water would be approximately 3000 psi, the same as that in the tank.

Is this right?

 

[JustAddWater]

Let's see... 6735 feet
204 atm equate to 3000 psi. Am I on the wrong track? It's my first guess, and I'll ponder it when I get home from work. :grad:

 

[scuba_adventurer]

What do you mean nothing happens? The gas in the tank will come out if the tank is held upright, but when you reach a 3000 psi ambient pressure it will just be the same volume as the tank. Now, if you hold the bottle upside down there should be nothing happening at 3000psi ambient.

 

[JustAddWater]

True...The air is still less dense than the water.

 

[TexasMike]

Originally posted by JustAddWater
Let's see... 6735 feet

Very close, but not quite correct. Extra gold star if you can figure out where (and why) your mistake is.

 

[JustAddWater]

Am I taking into account that my feet are dry on the first atm.?

 

[The Chairman]

204.08 atm

take away one atm for the atmosphere

203.08 atm X 33 fsw/atm = 6701.64 fsw

or

203.08 atm x 34 ffw/atm = 6904.72 ffw

 

[solodiver]

6701.6928 ft or 203.0816 ata +1 ata atmosphire total of 204.0816 ATA

 

[Rick Murchison]

Did y'all make a temperature correction in your calculations?
Rick