One atmosphere (1 atm) of pressure is equivalent to which of the following? 1. 29.9 in Hg 2. 14.7 lb/in2 3. 1034.0 g/cm2 4. 760.0 mm Hg

a. 1, 2, and 3
b. 2 and 4
c. 1 and 3
d. 1, 2, 3, and 4

ANS: D
At sea level, the average atmospheric pressure will support a column of mercury 76 cm (760 mm) or 29.9 in in height. If we also know that mercury has a density of 13.6 g/cm3 (0.491 lb/in3), then the average atmospheric pressure (PB) is calculated as follows:
cgs units: PB = 76 cm ? 13.6 g/cm3 = 1034 g/cm2
fps units: PB = 29.9 in ? 0.491 lb/in3 = 14.7 lb/in2