# Pressure

Pressure is the force per unit area.

This means that the pressure a solid object exerts on another solid surface is its in newtons divided by its area in square metres.

Pressure can be determined using the following equation.

$Pressure = \frac{{force}}{{area}}$

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

• The unit for pressure is the pascal ($$Pa$$).
• One pascal is equivalent to one newton per square metre.
• Atmospheric pressure is approximately $$1\times 10^{5} Pa = 100000 Pa$$.
Question

A cube-shaped box of $$10kg$$ is sitting on a level table. If the length of each edge of the box is $$0.2m$$, calculate the pressure the box exerts on the table.

Step 1

First calculate the weight of the box.

$Weight\,\,of\, \,box=mass\left ( m \right )\times\,gravitational\,\,field\,\,strength\left ( g \right )$

$Mass = 10$

$Gravity = 9.8$

$mg = 10 \times 9.8 = 98N$

Step 2

Then calculate the area of the box in contact with the table.

Area of box in contact with table

$= 0.2 \times 0.2 = 0.04{m^2}$

Step 3

Now calculate the pressure.

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

$P = \frac{{98}}{{0.04}}$

$= 2450Pa$