# Please explain the unit of pressure ( atmospheric pressure)?? Thank you so much.

Aug 10, 2017

Pressure, in simple terms, is a measure of the perpendicular force acting on a surface per unit area of the surface, and the simplified equation is

$P = \frac{F}{A}$

The base SI units of force are

• $\text{N}$ $= \left({\text{kg"*"m")/("s}}^{2}\right)$

The base SI units of area are

• ${\text{m}}^{2}$

So we perform the division of the units:

$P = \frac{F}{A} = \left(\left(\text{kg"*"m")/("s"^2))/("m"^2) = color(red)(ulbar(|stackrel(" ")(" ""kg"/("m"*"s"^2)" }\right) |\right)$

Or, in regular units,

color(red)(ulbar(|stackrel(" ")(" ""N/m"^2" ")|)

This unit is equivalent to the derived unit called the pascal:

$1$ $\text{N/m"^2 = color(blue)(1color(white)(l)"Pa}$

Often, atmospheric pressure is measured in either bars or atmospheres, so it's useful to know the conversion factors:

$1$ $\text{atm}$ $= 1.01325$ $\text{bar}$ $= 101325$ $\text{Pa}$

and that

$1$ $\text{bar}$ $= {10}^{5}$ $\text{Pa}$