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Name: Dee
Status: Educator
Age: 40s
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Question:
Why is the fluid in the hydraulic machine a liquid rather than a gas?



Replies:
Fluids are incompressible, relatively speaking, hence the pressure applied through the system is directly transmitted to the object which you want to lift. If you used a gas, you would waste a lot of energy compression the gas-hence the system would be inefficient.

H. Myron


Gases are compressible; liquids generally are not. Compressible fluids store energy. A hydraulic machine using a compressible working fluid would be dangerous and also difficult to manage. Try attaching your hands to a lawnmower with springs and cutting the grass that way.

Tim Mooney


Gases are more compressible than liquids. When you exert pressure on a gas, it can just scrunch down to occupy less volume. Liquids are not so compressible, so they can more reliably convert the motion of a piston at one end of the apparatus into motion of another piston at the other end.

Compressed gases can be used to drive machinery; lots of tools are driven by compressed air. They tend to involve letting the air escape at the businesss end, while hydraulic apparatus heep the fluid in a sealed environment.

Richard E. Barrans Jr., Ph. D.



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