- #1
lizzyb
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State the Problem
A gage is connected to a tank in which the pressure of the fluid is 42 psi above atmospheric. If the absolute pressure of the fluid remains unchanged but the gage is in a chamber where the air pressure is reduced to a vacuum of 25 inHg, what reading in psi will then be observed.
Related Equations, etc
Answer in back of book: 54.3 psi
Standard atmosphere at sea level: 14.696 psia (29.92 inHg)
Work Done So Far
1) Determine the absolute pressure using P_atm = 14.696 and P_gage = 42 psi
2) P_chamber = 25 * 14.696 / 29.92 = 12.279 psi
and manipulating (1) a bit:
Which isn't correct; how can I use equation (1) to determine P_gage correctly?
I suppose my problem is not having the correct relationship between P_atm and P_chamber; should I use:
but how do I justify equation (2)?
A gage is connected to a tank in which the pressure of the fluid is 42 psi above atmospheric. If the absolute pressure of the fluid remains unchanged but the gage is in a chamber where the air pressure is reduced to a vacuum of 25 inHg, what reading in psi will then be observed.
Related Equations, etc
Code:
P = P + P (1)
abs atm gage
Standard atmosphere at sea level: 14.696 psia (29.92 inHg)
Work Done So Far
1) Determine the absolute pressure using P_atm = 14.696 and P_gage = 42 psi
Code:
P = 14.696 + 42 = 56.696 psia
abs
2) P_chamber = 25 * 14.696 / 29.92 = 12.279 psi
and manipulating (1) a bit:
Code:
P = P - P = 56.696 - 12.279 = 44.417
gage abs chamber
Which isn't correct; how can I use equation (1) to determine P_gage correctly?
I suppose my problem is not having the correct relationship between P_atm and P_chamber; should I use:
Code:
'
P = P - P = 14.696 - 12.279 = 2.417 (2)
atm atm chamber
' '
P = P - P = 56.696 - 2.417 = 54.279
gage abs atm
but how do I justify equation (2)?