Depth pressure question

[TMHeimer]

I posed the same question as the OP a couple of years back. The answers were all the same, saying it makes no difference whether you're down 100' in the ocean (or lake) or inside a shaft that maybe is just wide enough to fit a diver. You'd think it would make a difference, but it doesn't. It's just what water that is directly above the diver that exerts the pressure. When you think about it, it has to be true. If you swam out from shore then descended 100' you would be under the same pressure as if you went out 20 miles and down 100'--yet 20 miles out (or in the middle of the Pacific) there is a heck of a lot more water all around you.

 

[windapp]

As strange as it seems, it will read whatever the vertical distance is between the diver and the top of the garden hose. In other words, around 100', even though the container itself is only 5' tall.

Doesn't seem strange at all. We are looking at the difference between force vs energy.

Imagine you have one of those camping water jugs with you. It is sealed with atomspheric air in it and you have it somehow rigidly supported so it won't collapse. Remove the supports, and the jug will start to collapse but, at the same time, the water will go down in the water hose to fill in the volume that is being left by the container. When the pressure gets low enough from the height of the water column changing, the jug will stop collapsing.

Do the same thing in the ocean and you have one collapsed container.

In both cases, we have the same force (pressure), but in case 2, we have a lot more energy available to do work.

 

[Charlie99]

I regularly collapse a flexible container underwater by removing its contents.

It's called Capri Sun juice drink.

 

[Stoy D Dabbs]

I took an empty Pepsi bottle filled with water down below 100 feet deep, and put air in it from my 2nd stage and close it off tight, and brought it up with me then I feel the pressure inside the bottle on the surface.

 

[Rich Keller]

Hello, I am not a diver at all. A bunch of us were talking and have a question. In the even that a person dived into a grain silo above ground. Let's say the silo was 110 ft tall and filled with water. Would you experience pressures just like as if you had dove 110ft below the surface of the ocean?

I have made a dive like that once, going down a pipe from the inside of a water tower to fix a valve at the bottom. The pressure comes from the weight of the water and the weight of the column of air on top of that water. Salt water adds .445psi per foot you descend into and fresh water adds .432psi per foot. Starting at 110ft above sea level the column of air would be slightly less then at sea level but not enough that it needs to be taken into consideration. So in your example the pressure would be 47.52psi from the weight of the water and 14.7psi from the weight of the air on top of that water.