Question

The atmospheric pressure and height of the barometer column is $${10}^{5}Pa$$ and $760mm$ respectively on the earth surface. If the barometer is taken to the moon, then what will be the column height?
A. zero
B. $76mm$
C. $126.6mm$
D. $760mm$

Answer 1

Hint: We know pressure in a barometer on earth is given by the formula
$p=\rho gh$
Where $\rho$ is the density.
$g$ is the acceleration due to gravity.
$h$ is the height of the column.
On earth the pressure is due to the presence of atmosphere. The reading that we get in the barometer corresponds to the atmospheric pressure
But on the moon there is no air or atmosphere.


Complete step by step answer:
A barometer is an instrument used to measure atmospheric pressure. Atmosphere is a layer of air surrounding the earth. This pressure tendency measured using a barometer can be used to forecast short term changes in the weather.
Given,
Atmospheric pressure on earth surface =${10}^{5}Pa$
The height of barometer on earth surface =$760mm$
We need to find column height on the moon.
We know pressure in a barometer on earth is given by the formula
$p=\rho gh$
Where $\rho$ is the density.
$g$ is the acceleration due to gravity.
$h$ is the height of the column.
On earth the pressure is due to the presence of the atmosphere. The reading that we get in the barometer corresponds to the atmospheric pressure.
But on the moon there is no atmosphere. So, there will be no atmospheric pressure
Thus pressure, $p=0$.
That is, $\rho gh=0$
$\Rightarrow h=0$
So, the height of the column will be zero on the moon.

Note: If there was atmosphere on moon(just in case) then we would have to calculate the gravity on moon, on moon gravity is less than that on earth, hence it would take more height than 760mm of Hg to record the same pressure.