Question

A column of air 1 sq. cm. in cross-sectional area extending from sea-level to the top of the atmosphere weights approximately ______.

• A. 933 g wt
• B. 1033 g wt
• C. 1136 g wt
• D. 1360 g wt

Answer 1

The correct option is B 1033 g wt

1033 g wt

Air pressure at sea level is about 101 000 Pa. A Pa (pascal), by definition, is a newton per square meter.

So the weight, force of that column which is 1 square meter in cross-section area is 101000 newtons.

There are 10000 cm² per m², so we get

the weight, force of that column 1 square cm in cross-section area is 10.1 newtons ⬅

Using F = ma or Weight = mass x acceleration of gravity,

10.1 newtons corresponds to a mass of 10.1 N / 9.8 = 1.03 kg ⬅

that is approximate and does not account for the weight decreasing as you go up in altitude. But most of the air is at low altitudes, so it's close.