What is Pressure?

In short

Pressure is the force acting on each unit of area, $P = \dfrac{F}{A}$ . Its unit is the pascal (Pa), which is one newton per square metre.

In simple words

A force on a small area gives a large pressure, which is why a knife cuts and a nail goes in. In a liquid, the pressure at depth $h$ is $P = P_0 + \rho g h$ . A barometer measures atmospheric pressure, using a column of mercury about $760\ \text{mm}$ high at sea level. This corresponds to $1.013 \times 10^{5}\ \text{Pa}$ .

Example

A person of $60\ \text{kg}$ stands on two feet with a total area of $0.04\ \text{m}^2$ . The pressure on the ground is $\dfrac{60\ \text{kg} \times 9.8\ \text{m/s}^2}{0.04\ \text{m}^2} = 14\,700\ \text{Pa}$ .

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