The behaviour of gases is described in terms of the kinetic theory, which considers the motion of molecules in the gas. The gas law links pressure, volume and temperature.

Part of

Pressure is the force per unit area.

This means that the pressure a solid object exerts on another solid surface is its weight 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 mass \(10kg\) 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.

\[P = \frac{F}{A}\]

\[P = \frac{{98}}{{0.04}}\]

\[= 2450Pa\]