Member Login
Posted: 6/12/2002 11:07:58 AM EDT
How much force does water exert if you are 40 feet down? 60?


That's PERSEC, not OPSEC. AvengeR15

Water gains or loses .433 psi per ft.
HTH gains going down, loses going up 


hmmmmm....it's been many, many years since my basic SCUBA course, but if I remember correctly, for every 33 feet you descend, the pressure increases by 1 atmosphere. So, at 40 feet you'd be at a little over 2 atmospheres of pressure, at 60 feet you'd be at almost 3 atmospheres.... Basically, what this means is that if you are sitting in 33 feet of water, take a full lungfull of air from a tank and ascend while holding your breath...then the amount of air in your lungs would double by the time you reach the surface....result would be a blown lung or an embolism....neither of which is desireable :) 


Originally Posted By Polyak: Water gains or loses .433 psi per ft. HTH gains going down, loses going up View Quote Going under is exponetial. GG 


Sorry, I guess I read the question wrong. I thought you were asking about water velocity pressure.



14.7 psi at 33 feet



Originally Posted By TalonJ: 14.7 psi at 33 feet View Quote 

That's PERSEC, not OPSEC. AvengeR15

Isn't 14 and something psi the air pressure at sea level?
Yep I think its 14.7 Water info I remember from SCUBA diving 14.7 psi at 33 feet = .445 psi per foot checks pretty close to Polyaks answer Water gains or loses .433 psi per ft. 


Originally Posted By Keith: Basically, what this means is that if you are sitting in 33 feet of water, take a full lungfull of air from a tank and ascend while holding your breath...then the amount of air in your lungs would double by the time you reach the surface....result would be a blown lung or an embolism....neither of which is desireable :) View Quote So, holding your breath while under water is a bad thing? [shock] 


No, the problems potentially arise in diving with pressurized air only.



Using these non SI units, and assuming that we're talking about fresh water:
[Edited because I really ought to express all units:" 34 feet of depth in water=1 Atmosphere, 1 Atmosphere=14.7 pounds/square inch (psi) 14.7psi/34feet of depth=.432 psi/foot of depth So, at 40 feet: 40feet*.432psi/foot=17.28 psi This is the gauge (hydrostatic) pressure. The absolute pressure must include the column of air that is stacked on the water, so we add 17.28psi+14.7psi=31.98 psia (pounds/square inch abosolute) 


1 psi per 2.3 ft. of water or 0.435 psi per ft of water.


"The problem with Socialism is that you eventually run out of other people's money." Margaret Thatcher

Water pressure at depth is linear, because a liquid can’t be compressed. About 32psi at 40 feet and about 40.5psi at 60 feet. R/K 


I should quantify that answer includes atmospheric pressure and like IMHO pointed out, would be absolute pressure. 


As mentioned before...
1 atm= 14.7 psi (sea level) 2 atm= 29.4 psi (33 feet deep) 3 atm= 44.1 psi (66 feet deep) 4 atm= 58.8 psi (99 feet deep) This information was obtained from [u]Jeppesen's Open Water Sport Diver Manual[/u] that was given to me when going through my SCUBA lessons. Hope this helps!!! 


I think I will call my sister tomorrow about getting SCUBA cert'd. [:)]


That's PERSEC, not OPSEC. AvengeR15

What has always puzzled me is to see fish swimming about in the oceans deepest waters and knowing at those same depths a steel hulled submarine would be crushed. I know there is a scientific/mathematical answer, but It still amazes me.



Originally Posted By AmOTramp: What has always puzzled me is to see fish swimming about in the oceans deepest waters and knowing at those same depths a steel hulled submarine would be crushed. I know there is a scientific/mathematical answer, but It still amazes me. View Quote I believe it's due to that the fish has equal internal and external pressure. Whereas the sub requires 'air' within, hence the pressure difference. 


Thank your Older_Crow. AmOTramp



AR15.COM is the world’s largest firearm community and is a gathering place for firearm enthusiats of all types.
From hunters and military members, to competition shooters and general firearm enthusiats, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 19962020 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.