Question

Pascal’s law involves the use of the word- “enclosed fluid” so how can we apply Pascal’s law in the case of atmospheric pressure?

Answer 1

Pascal's law tells us about the pressure exerted by an enclosed fluid. The pressure depends on the force as well as the area. When a fluid is enclosed in a container, the pressure exerted by it is the same in all the directions. Atmospheric pressure is the pressure exerted by the air molecule on all the bodies.

Complete answer:
Pascal law states that when pressure is applied to enclosed fluid, it will be transmitted in all the directions and to the walls of the container without any change in the magnitude.
Therefore, the pressure is given as-
$P=\dfrac{F}{A}$
Here, $P$ is the pressure
$F$ is the force
$A$ is the area of cross section
Since the atmosphere encloses the Earth, it is held down by the gravitational pull. So the atmosphere cannot get out of the gravitational pull unless the air molecules acquire escape velocity.
So we can say the atmosphere can be imagined as a shell around the Earth in which the air molecules are enclosed.
Therefore, we can say that the atmosphere is enclosed around the Earth due to the gravitational field of the Earth and hence Pascal's law can be extended to the atmospheric pressure.

Note:
The atmospheric pressure varies with height. A height from the sea level rises, the pressure due to the atmosphere decreases and vice versa. The pressure exerted by the fluids is due to the collision of the molecules of the fluid with the container in which it is enclosed. The SI unit of pressure is Pascal.