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

##### 1 Answer

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 = F/A#

The base SI units of ** force** are

#"N"# #= ("kg"*"m")/("s"^2)#

The base SI units of ** area** are

#"m"^2#

So we perform the division of the units:

#P = F/A = (("kg"*"m")/("s"^2))/("m"^2) = color(red)(ulbar(|stackrel(" ")(" ""kg"/("m"*"s"^2)" ")|)#

Or, in regular units,

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

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

#1# #"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# #"atm"# #= 1.01325# #"bar"# #= 101325# #"Pa"#

and that

#1# #"bar"# #= 10^5# #"Pa"#