[CS_SJ (OP)]

Hello,

I'm a little confused about water pressure at extreme depths. Let's say that you attached a 100 lb. weight to a barrel, and the barrel had enough barely enough buoyancy to be able to just hold that weight at the surface (see Figure 1.)

Then, you took the same barrel (a strong barrel that won't compress) and you put it at the bottom of the ocean 1000 feet down (see Figure 2) would the pressure down there give the barrel more lifting power? Would that same barrel be able to lift 1000 lbs. down there? 2000 lbs.?

Or, would the pressure on top of the barrel equal it all out and even 1000 feet down, all the barrel could lift is 100 lbs.?


Extra question: if the barrel at the bottom of the ocean WOULD have more lifting power, does that mean it would accelerate like a rocket off of the bottom of the ocean, and then slow down the closer it got to the surface?

Thank you,

- DJ

[Halc]

(a strong barrel that won't compress)

Oh good, because a bag of air loses buoyancy (lifting power) the more it compresses with depth.

Or, would the pressure on top of the barrel equal it all out and even 1000 feet down, all the barrel could lift is 100 lbs.?

Pretty much that one. It all has to do with weight of displaced water, not of pressure at all, so 1000 ft down it would lift a small bit more than 100 lb since water is a bit more dense down there.

Extra question: if the barrel at the bottom of the ocean WOULD have more lifting power, does that mean it would accelerate like a rocket off of the bottom of the ocean, and then slow down the closer it got to the surface?

It has a terminal velocity just like a falling thing, and yes, if it somehow had significantly more force at greater depth, then it would slow as that force decreased with altitude, just like a Mylar balloon slows its ascent as the air gets thinner. A Mylar balloon doesn't expand significantly with change of pressure, unlike a latex balloon which stretches, or a helium bag like the ones used by the guys setting distance records, which fills with altitude, but doesn't stretch.