Question

The atmospheric pressure at the surface of the earth is about
A. ${{10}^{2}}N{{m}^{-2}}$
B. ${{10}^{5}}N{{m}^{-2}}$
C. ${{10}^{-3}}N{{m}^{-2}}$
D. ${{10}^{-5}}N{{m}^{-2}}$

Answer 1

Hint: Atmospheric pressure which is also called barometric pressure, by definition is the pressure exerted by the atmospheric column or the air column that is present above the specified area. Atmospheric pressure at sea level is one standard atmosphere. On the surface of the earth the highest atmospheric pressure is found to be at the sea level.

Formula used: $1Pa=1N{{m}^{-2}}$

Complete step by step answer:
We know many different systems of units in which we could express the atmospheric pressure. The standard atmospheric pressure is given in different units as the following: 760mm of mercury,$1013.25\times {{10}^{3}}$ dynes per square centimeter, 14.70 pounds per square inch, 1013.25 millibars, or simply one standard atmosphere which is 101.325 kilopascals.
But in this question all the approximated values are given in$N{{m}^{-2}}$, so, we have to find the value of one standard atmosphere in$N{{m}^{-2}}$.
But we know that, $1Pa=1N{{m}^{-2}}$
Also, One standard atmosphere= 101.325 kilopascals
$101.325KPa=101.325\times {{10}^{3}}N{{m}^{-2}}$
Therefore, atmospheric pressure at sea level measured in $N{{m}^{-2}}$ is$1.013\times {{10}^{5}}N{{m}^{-2}}$ , which could be approximated as${{10}^{5}}N{{m}^{-2}}$. Since, the highest atmospheric pressure on the surface of earth is found to be at the sea level, we could say that, the atmospheric pressure at the surface of the earth is approximately${{10}^{5}}N{{m}^{-2}}$.

So, the correct answer is “Option B”.

Note: We know that the atmospheric pressure just like any pressure is defined as the force acting per unit area. But, here the source of the force is the atmospheric column or the air column above a body. Mainly, it is measured using a mercury barometer, where the height of a column of mercury balances the weight of the column of atmosphere and hence measurement is taken.