Does Mass Occupying Volume in a Compressed Air System Transfer Energy

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SUMMARY

The discussion centers on the energy transfer dynamics within a compressed air system involving a suspended mass of 10 cubic meters at 20 atm pressure. Upon release, the mass converts its potential energy into kinetic energy as it falls into water, causing the water level to rise. The pressure inside the vessel does not decrease by the volume of the mass multiplied by the pressure, as the air volume remains constant before and after the mass submerges. The total energy in the system can be expressed mathematically, factoring in potential energy (PE), kinetic energy (KE), and heat generated upon impact.

PREREQUISITES
  • Understanding of basic physics concepts such as potential energy (PE) and kinetic energy (KE).
  • Familiarity with the ideal gas law and pressure-volume (PV) relationships.
  • Knowledge of fluid dynamics, particularly how submerged objects affect water levels.
  • Basic mathematical skills to express energy equations and conversions.
NEXT STEPS
  • Explore the ideal gas law and its applications in compressed air systems.
  • Learn about energy conservation principles in mechanical systems.
  • Investigate fluid dynamics related to submerged objects and buoyancy.
  • Study the effects of air resistance on falling objects in different mediums.
USEFUL FOR

Engineers, physicists, and students interested in mechanics, fluid dynamics, and energy transfer in compressed air systems will benefit from this discussion.

genergy
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In a compressed air space there is a suspended mass with 10 cubic meters volume. The pressure vessel is 20 atm. The suspended mass is suspended 100 meters over water that is kept at bay by the air pressure inside the vessel.

The moment the mass is released its potential energy converts to kinetic energy.

There is a door that closes off the 10 cubic meters of volume space so that there is 20 atm of pressure inside (E=PV).

The mass falls and impacts the water and submerges.
The water level rises.

Does the pressure inside the vessel decrease by 10m3 x 20 atm?

Is the PV energy inside the closed space equal to 10m3 x 20 atm minus air resistance?

Can this be written in math?
Can this idea be expressed mathematically?
 
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genergy said:
In a compressed air space there is a suspended mass with 10 cubic meters volume. The pressure vessel is 20 atm. The suspended mass is suspended 100 meters over water that is kept at bay by the air pressure inside the vessel.

The moment the mass is released its potential energy converts to kinetic energy.

There is a door that closes off the 10 cubic meters of volume space so that there is 20 atm of pressure inside (E=PV).

The mass falls and impacts the water and submerges.
The water level rises.

Does the pressure inside the vessel decrease by 10m3 x 20 atm?

Is the PV energy inside the closed space equal to 10m3 x 20 atm minus air resistance?

Can this be written in math?
Can this idea be expressed mathematically?

The water will not be kept "at bay" by the air if there is no gravity. Think of what happens to water in the Space Shuttle or Space Station in orbit...

And if this experiment is carried out on the surface of the Earth, the volume of the air stays the same before and after the mass goes underwater. The surface of the water only rises because of the volume of the mass that is submerged, so the total volume of the water + object is constant.
 
What berkeman said. The volume of air stays the same. You just traded the volume occupied by the mass (10cubic meters) for the volume occupied by the water (10 cubic meters).

The mass had some PE which was converted to KE and then to heat when it hit the water so I suppose the water warmed slightly.
 

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