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 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/m2

f is the unit of force in newtons

a is the unit of area in m2

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 m2. What is the pressure?

force ÷ area = pressure

20 ÷ 2 = 10 N/m2

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.