Units of Measurement/Pressure

This figure shows pressure exerted by particle collisions inside a closed container. The collisions that exert the pressure are highlighted in red.

Pressure is the force per unit area applied in the direction perpendicular to a surface. Mathematically, pressure is defined as

$P=\frac{dF}{dA}$

where:

P is pressure

F is the component of force perpendicular to the surface

A is the area of the surface

When a force is constant over an area, the pressure acting on that area is simply

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

It can be given the units of N.m^-2. Pressure is a scalar quantity, thus it acts in all directions at any given point. In order for pressure to create a force, the pressure must be integrated over some area.