Pressure

Pressure

Pressure is the amount of force pushing on an area of a surface.
Pressure is caused by any contact force pushing on an object.
Pressure is force acting normal per unit area.

In solids

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

$P_{max} = \frac{F}{A_{min}}$

$P_{min} = \frac{F}{A_{max}}$“

In liquids

$P = h \rho g$

In U-tube

Given the $P_{\text{atm}} = 76 \, \text{cm Hg}$. Calculate the $P_g$ in

a) $P = 96 \, \text{cm Hg}$

b) $P = 130560 \, \text{Pa}$ (as density of Hg is $13600 \, \text{kg/m}^3$)

a) $P_g' = P_{\text{atm}} + \Delta h = 76 + 20 = 96 \, \text{cm Hg}$

b) $P_g = P_g' \times 13600 \times 10 = 130560 \, \text{Pa}$

Key Words on Pressure

English Term	Meaning
Force	A push or a pull on a body
Weight	Force due to gravity
Area	Surface size
Pressure	Force acting normally per unit area
Pascal (Pa)	Unit of pressure