Question

One can consider atmospheric pressure at a particular location as arising from the force exerted by a column of air reaching from that location into space. At higher altitudes, the mass of the air in the column is _____ than the mass of the column at lower altitudes. Thus, atmospheric pressure _____ as altitude increases.

a) Less, decreases
b) More, decreases
c) Less, increases
d) More, increases

Answer 1

At higher altitudes, there is less atmospheric pressure because the mass of the air in the column above is less, causing the pressure to decrease.

Step-by-step explanation:

At higher altitudes, the mass of the air in the column is less than the mass of the column at lower altitudes. Thus, atmospheric pressure decreases as altitude increases. The correct answer to the question is a) Less, decreases.

One way to understand this is by considering how atmospheric pressure is caused by the weight of the column of air above us. At sea level, the column of air stretches all the way to the edge of the atmosphere, exerting a pressure of about 760 mm Hg due to its mass. As we ascend, the column of air above us becomes shorter and, therefore, lighter, resulting in less pressure exerted. This is why on the summit of Mt. Everest the atmospheric pressure is only about 253 mm Hg. The Ideal Gas Law and the fact that atmospheric pressure is another example of pressure due to the weight of a fluid help explain the variation of pressure with altitude.