Measuring Atmospheric Pressure with a Barometer

Determine the atmospheric pressure at a location where the barometric reading is 740 mm Hg and the gravitational acceleration is g = 9.81 m/s². Assume the temperature of mercury to be 10°C, at which its density is 13,570 kg/m³.

Question

Measuring Atmospheric Pressure with a Barometer

Determine the atmospheric pressure at a location where the barometric reading is 740 mm Hg and the gravitational acceleration is g = 9.81 m/s². Assume the temperature of mercury to be 10°C, at which its density is 13,570 kg/m³.

Accepted Answer

The barometric reading at a location in height of mercury column is given. The atmospheric pressure is to be determined.
Assumptions The temperature of mercury is 10°C.
Properties The density of mercury is given to be 13,570 kg/m³.
Analysis From Eq. 1–26, the atmospheric pressure is determined to be

[latex] P_{ atm }= ho g h [/latex] (1–26)

[latex]\begin{aligned}P_{ atm } &= ho g h \&=\left(13,570 kg / m ^{3} ight)\left(9.81 m / s ^{2} ight)(0.74 m )\left(\frac{1 N }{1 kg \cdot m / s ^{2}} ight)\left(\frac{1 kPa }{1000 N / m ^{2}} ight) \&=98.5 kPa\end{aligned}[/latex]

Discussion Note that density changes with temperature, and thus this effect should be considered in calculations.

Question 1.8: Measuring Atmospheric Pressure with a Barometer Determine th...

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