Question

The column of a mercury barometer is calibrated in linear units (such as inches or millimeters) and thus the air pressure observed on such a barometer is reported in terms of these linear units. This measurement of pressure can be converted to other common pressure units. Some conversion factors are shown here.

1mm Hg = 1torr

1 atm = 760mm Hg

1 atm = 1.01325 bar

1 Pa = 10^-5 bar

1 in = 2.54 cm

1 cm = 10 mm

754 753

Part A:

The barometer shown here (Figure 1) measures atmospheric pressure in millimeters of mercury (mmHg). According to this barometer, what is the atmospheric pressure P in inches of mercury (inHg)?

Express your answer in inches of mercury using five significant figures.

Part B:

At a pressure of 941 mbar , what would be the corresponding height of the mercury in the column of a mercury barometer?

Express your answer numerically in millimeters of mercury.

Answer 1

Part A : inches of mercury = 29.661

Part B : height of mercury in millimeters = 705.8

Explanation

Part A

In the given figure, height of mercury = 753.4 mm

height of mercury = 753.4 mm * (1 cm / 10 mm) * (1 in / 2.54 cm)

height of mercury = (753.4 mm / 25.4) in

height of mercury = 29.661 in

Part B

pressure = 941 mbar = 0.941 bar

pressure = 0.941 bar * (1 atm / 1.01325 bar) * (760 mmHg / 1 atm)

pressure = (0.941 * 760 / 1.01325) mmHg

pressure = 705.8 mmHg