Pressure is calculated by dividing force by area. There is more pressure at greater depths in liquids and in denser materials. Manometers and barometers measure pressure.

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.

\[pressure=\frac{force}{area}\]

\[p=\frac{f}{a}\]

where:

*p* is the unit of pressure in pascals. One pascal is 1 N/m^{2}

*f* is the unit of force in newtons

*a* is the unit of area in m^{2}

Area is calculated by the following equation:

area = length × width

The units of length and width are metres.

- Question
A force of 20 N acts over an area of 2 m

^{2}. What is the pressure?force ÷ area = pressure

20 ÷ 2 = 10 N/m

^{2}

To **increase pressure** - increase the force or reduce the area the force acts on. To cut up your dinner you can either press harder on your knife or use a sharper one (sharper knives have less surface area on the cutting edge of the blade).

To **reduce pressure** - decrease the force or increase the area the force acts on. If you were standing on a frozen lake and the ice started to crack you could lie down to increase the area in contact with the ice. The same force (your weight) would apply, spread over a larger area, so the pressure would reduce. Snow shoes work in the same way.