Question

What is atmospheric pressure?

Answer 1

Pressure is defined as the force per unit surface area. There are different units to measure pressure. Atmospheric pressure is the force that is exerted on the ground by the air above it, when it is attracted by gravity. The units of atmospheric pressures is atmosphere (atm)

Complete Step By Step Answer:
The weight exerted by the atmosphere on the earth is the atmospheric pressure and it is measured in various units other than pascals. This pressure is maximum on the earth’s surface and reduces as we increase the altitude. At sea level the density of the atmosphere is highest and this density reduces as the altitude increases. The no. of molecules of air are also less at higher altitudes hence the pressure is less.
The atmospheric pressure is also approximately measured by the hydrostatic pressure, which is the pressure due to the weight of the air just above the measurement point.
The atmospheric pressure is measured using an instrument called a Barometer. Barometric height is the unit used to measure the atmospheric pressure. The height of the mercury is used as the unit to measure atmospheric pressure. The atmospheric pressure is also known as the Barometric pressure.
The pressure using the barometer is measured by using the formula: $P = \rho gh$
Where P is the pressure, $\rho$ is the density, g is the gravity constant and h is the height of the mercury in the barometer.

Note:
The atmospheric pressure is the maximum at sea level as the atmospheric depth is maximum at the sea level. Below the sea level the pressure increases more drastically as the water also exerts pressure and the pressure increases by a rate of 1 atm for every 10m depth under the sea level.