Lifting power of Compressed Air

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SUMMARY

The lifting power of compressed air in water is determined by both its volume and the surrounding pressure. A bell containing 2 cubic feet of air can lift 128 lbs at the ocean's surface due to the displacement of saltwater, which weighs 64 lbs per cubic foot. However, as the bell descends to depths of 33 feet and 99 feet, the volume of the air compresses, reducing its lifting capacity to 64 lbs and 32 lbs, respectively. This principle remains consistent regardless of whether the bell is submerged in the ocean or in a cylindrical water tower filled with saltwater at sea level.

PREREQUISITES
  • Understanding of buoyancy principles
  • Knowledge of gas laws, particularly Boyle's Law
  • Familiarity with fluid density, specifically saltwater density
  • Basic concepts of pressure and atmospheric conditions
NEXT STEPS
  • Research Boyle's Law and its applications in fluid mechanics
  • Explore the principles of buoyancy and Archimedes' principle
  • Study the effects of pressure on gas volume in underwater environments
  • Investigate the differences in fluid density between freshwater and saltwater
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Marine engineers, physicists, and anyone interested in the principles of buoyancy and fluid dynamics in underwater environments.

Kalagan
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Hi,

Question: Is the Lifting Power of Air in Water solely based on its Volume or does the pressure of the Air factor in?

As an example, in Salt water if you have a Bell with 2 Cubic ft of Air in it, at the Oceans Surface it can lift 128 Lbs, because air can lift the amount of Water it displaces, which in this example is 2 Cubic Ft and Salt water is 64 Lbs/Cubic ft. so it can lift 128Lbs.

But what happens if you bring that Bell down to 33ft (1 Atmosphere), which will compress the Air to 1/2 its Volume, so at 33ft the Volume of the Compressed Air will now be 1 cubic ft. Would that Bell now only be able to lift 64 Lbs?

What happens if you bring that Bell to 99ft deep or 4 Atmospheres, the Volume is now 25% of its Volume at the Surface, so that same Bell can now only lift 32Lbs?

If that logic holds true in the Ocean, do any of those calculations change if the same Bell is placed in a 100ft Cylindrical Water Tower filed with Salt Water placed on the Ground at Sea Level?

Thanks for any Input.
Kalagan
 
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Welcome to PF.

You understand the issue perfectly... so the answer to your your last question is no.
 

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