Question

A column of air 1 sq.cm. in a cross-sectional area extending from sea-level to the top of the atmosphere weights approximately_________.
A.933g wt
B.1033g wt
C.1136g wt
D.1360 g wt

Answer 1

Hint: Air pressure is the force put forth on a surface by the air above it as gravity pulls it to Earth. The pressure of the air molecules undergo changes as one moves upward from sea level into the atmosphere.

Complete Answer:
- A cross-sectional area of 1 square centimetre when calculated from mean sea level , has a mass of about 1.03 kg and puts out a force of about 10.1 newtons, arising in a pressure of 10.1 N/cm².

As elevation increases, atmospheric pressure decreases with increasing elevation. Pressure estimates force per unit area, with SI units of Pascals.
1 pascal = 1 newton per sq. metre.

A Pa (pascal) is defined as newton per square meter.
So the force of that section which is 1 square meter in the cross-section area is 101000 newtons.
There are 10000 sq. cm per sq. m, so we get
The weight force of that column 1 square cm in the cross-section area is 10.1 newtons.

Using F = ma / Weight = mass x acceleration of gravity,
10.1 newtons approximates to a mass of 10.1 N / 9.8 = 1.03 kg .

It 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 near.

Hence, the correct option is B.

Note: Atmospheric pressure is also known as barometric pressure. The standard atmosphere is a unit of pressure which is characterized as 101,325 Pa, which is identical to 760 mm Hg. The atm unit is approximately the same as the mean sea-level atmospheric pressure on Earth, that is, the Earth's atmospheric pressure at sea level is roughly 1 atm.