Pressure in a certain tank is 55.8 Pa

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Discussion Overview

The discussion revolves around the interpretation of pressure measurements in a tank, specifically focusing on a stated absolute pressure of 55.8 Pa and the implications of negative pressure values. The scope includes conceptual clarification and technical reasoning regarding absolute and gauge pressure.

Discussion Character

  • Conceptual clarification, Debate/contested, Technical explanation

Main Points Raised

  • One participant questions the validity of stating a pressure of 55.8 Pa (abs), suggesting it implies a condition that seems impossible.
  • Another participant notes that a pressure of 55.8 Pa indicates a (partial) vacuum, which may be acceptable in specific contexts like a vacuum brake system, but unlikely for a household water tank.
  • A participant highlights a potential error in the pressure value, suggesting it should be -55.8 Pa (abs), questioning the feasibility of a pressure below absolute zero.
  • Some participants assert that negative absolute pressure values are nonsensical, while others discuss the implications of gauge pressure readings, such as -4.65 psig translating to a plausible absolute pressure.
  • There is a mention of gauge pressure being negative in certain contexts, such as between two tanks, but clarity in the question is deemed necessary.
  • One participant expresses agreement with the notion that negative absolute pressure values are not feasible, reinforcing the idea that the original statement may be flawed.

Areas of Agreement / Disagreement

Participants generally disagree on the feasibility of the stated absolute pressure of 55.8 Pa, with some asserting it is impossible while others suggest it could be contextually valid. The discussion remains unresolved regarding the interpretation of negative pressures.

Contextual Notes

The discussion includes assumptions about the definitions of absolute and gauge pressure, as well as the context in which the pressures are measured. There are unresolved questions about the clarity of the original pressure statement and its implications.

Jason03
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I am trying to figure if there is anything wrong with this statement.

The pressure in a certain tank is 55.8 Pa (abs)


55.8 Pa is about .008 Psi...and the gage pressure would be -100.9 kpa...

...I wouldn't think this condition would be possible
 
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Depends on the tank, it means it is under (partial) vacuum.
So ok for a vacuum brake system on a truck - unlikely for a water tank in a house.

I would check they meant abs rather than gauge and they hadn't missed a prefix on the Pa.
 


The questions are supposed to be answered True or False stating why its false...or how it could be true...and it states the pressure in Pa (abs)...but i did notice one thing I missed...its -55.8 Pa (abs)...so this pressure would be below a perfect vaccumm which doesn't seem possible to me...


At zero pressure using absolute pressure you have a perfect vacuum...so can you go below that?

and the next question says a certain tank has a pressure of -4.65 psig. giving you a absolute pressure of 9.95psi...which I would think would be more of a possiblitly
 
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You can't have -55.8Pa abs, that's less than nothing = silly.
-4.65psig = 9.95psi (abs) is true (give or take the odd least sig figure)
 


Yea that's what i figured for the 55.8 Pa when I noticed the negative sign...and it would be the same if you had -150 kpa gage which would be -48.9Kpa absolute...which would = silly again...
 


Gauge could be -150 kpa if it was between two tanks.
So one tank with 1000 kPa and another with 850kPa you could have a gauge reading of -150kPa but the question would have to make that clear.
 


Yea that makes sense...but the question states that its the pressure of one tank...
 

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