What is (Mechanical) Pressure?
Important Formula
What do the formula symbols mean?
Pressure
$$ \mathit{\Pi} $$ Unit $$ \mathrm{Pa} = \frac{ \mathrm{N} }{ \mathrm{m}^2 } $$Force
$$ \class{red}{F} $$ Unit $$ \mathrm{N} $$Area
$$ A $$ Unit $$ \mathrm{m}^2 $$The pressure \( \mathit{\Pi} \) is defined as the force \(F\) acting perpendicularly on a surface area \(A\):
The pressure is abbreviated here with the Greek capital letter \( \mathit{\Pi} \) (pronounced: Pi). Sometimes the pressure is also abbreviated with the letter \(p\), but that is avoided here because \(p\) is already used for the momentum.
The force \(F\) has the unit \( \mathrm{N} \) (newtons) and stands for the unit \( \frac{\mathrm{kg} \, \mathrm{m}}{\mathrm{s}^2} \) (kilograms per second squared). The area \(A\) has the unit \( \mathrm{m}^2\) (square meter). Because of equation 1
the pressure \( \mathit{\Pi} \) must have the unit \( \frac{\mathrm{N}}{\mathrm{m}^2} \). Newton per square meter is usually abbreviated with the unit \( \mathrm{Pa} \) (Pascal) for pressure.
From the definition 1
of pressure, we can read the following information:

The larger the force \(F\), the larger the pressure \(\mathit{\Pi}\).

The smaller the surface \(A\) on which the force is applied, the greater the pressure \(\mathit{\Pi}\).
There are several special names of pressure, but they can all be traced back to the definition 1
. Here are some examples:

Air pressure  is caused by the gravitational force exerted by the air. The air pressure at sea level is \( 10^5 \, \mathrm{Pa} \). Therefore, the unit "bar" is usually used for air pressure: \( 1\, \mathrm{bar} = 10^5 \, \mathrm{Pa} \).

Gravity pressure  is also caused by the gravitational force exerted by a liquid or gas.