Pressure in a certain tank is 55.8 Pa

[Jason03]

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

 

[mgb_phys]

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.

 

[Jason03]

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

 

[mgb_phys]

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)

 

[Jason03]

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...

 

[mgb_phys]

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.

 

[Jason03]

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