1–43 Determine the atmospheric pressure at a location
where the barometric reading is 750 mm Hg. Take the density
of mercury to be 13,600 kg/m3.
ANS
1-43The barometricreading ata location isgiven inheightof mercury column. The atmospheric pressure
is tobedetermined.

1–42

1–42 The water in a tank is pressurized by air, and the
pressure is measured by a multifluid manometer as shown in
Fig. P1–42. Determine the gage pressure of air in the tank if
h1 0.2 m,h2 0.3 m, and h3
0.46 m. Take the densities
of water, oil, and mercury to be 1000 kg/m
3, 850 kg/m3, and13,600 kg/m3, respectively.

ANS

1-42 The pressure ina pressurized water tank ismeasured bya multi-fluid manometer. The gage pressure 

ofair inthe tankis tobedetermined. 

Assumptions The air pressure inthe tankis uniform(i.e., its variationwithelevationis negligible due to its 

low density), and thus we can determine the pressure at the air-water interface. 

Properties  The densities of mercury, water, and oil are given to be 13,600, 1000, and 850 kg/m

3

, 

respectively. 

AnalysisStarting with the pressure at point 1 at the air-water interface, and moving along the tube by 

adding (as we go down) or subtracting (as we go up) the  gh ρ terms until we reach point 2, and setting the 

result equal to Patm

since the tube isopen tothe atmosphere gives 

1–41E

1–41E A manometer is used to measure the air pressure in
a tank. The fluid used has a specific gravity of 1.25, and the
differential height between the two arms of the manometer is
28 in. If the local atmospheric pressure is 12.7 psia, determine the absolute pressure in the tank for the cases of the
manometer arm with the (a) higher and (b) lower fluid level
being attached to the tank.
ANS
1-41E The pressure ina tank ismeasured witha manometer bymeasuring the differentialheightof the
manometer fluid. The absolutepressure inthe tank isto be determined for the cases of the manometer arm
withthe higher and lower fluid levelbeing attached tothe tank .

1–40

1–40 A vacuum gage connected to a chamber reads 35 kPa
at a location where the atmospheric pressure is 92 kPa.
Determine the absolute pressure in the chamber.
ANS

1–39C

1–39C Consider two identical fans, one at sea level and the
other on top of a high mountain, running at identical speeds.
How would you compare (a) the volume flow rates and
(b) the mass flow rates of these two fans?
ANS
1-39CThe densityof air atsea levelishigher than the densityof air on top of a high mountain. Therefore,
the volume flow rates of the two fans running at identical speeds will be the same, but the mass flow rate of
the fanat sea level will behigher.

1–38C

1–38C Express Pascal’s law, and give a real-world example
of it.
ANS
1-38C  Pascal’s principlestates that the pressure appliedtoaconfinedfluidincreases the pressure
throughout by the same amount. Thisisa consequence of the pressure ina fluid remaining constantinthe
horizontaldirection. An example of Pascal’s principle isthe operation of the hydrauliccar jack.

1–37C

1–37C A tiny steel cube is suspended in water by a string.
If the lengths of the sides of the cube are very small, how
would you compare the magnitudes of the pressures on the
top, bottom, and side surfaces of the cube?
ANS
1-37CIf the lengths of the sides of the tinycube suspended inwater by a string are very small, the
magnitudes ofthe pressures onall sides ofthe cubewill bethe same.