Pressure (Edexcel IGCSE Physics)

• Pressure is defined as

The concentration of a force or the force per unit area

• Pressure, force and area are related by the equation:

• Where:
  • P = pressure, measured in pascals (Pa)
  • F = force, measured in newtons (N)
  • A = cross-sectional area, measured in metres squared (m²)

• The cross-sectional area is the area that the force is applied at right angles to 

Pressure, force, area formula triangle

A formula triangle can help rearrange the pressure equation

• For more information on how to use a formula triangle refer to the revision note on speed

Examples of applications of pressure

• For example, when a drawing pin is pushed downwards:
  • It is pushed into the surface, rather than up towards the finger
  • This is because the sharp point is more concentrated (a small area) creating a larger pressure

Applying a force to a drawing pin

When you push a drawing pin, it goes into the surface (rather than your finger)

• Example 1: Tractors
  • Tractors have large tyres
  • This spreads the weight (force) of the tractor over a large area
  • This reduces the pressure which prevents the heavy tractor from sinking into the mud

• Example 2: Nails
  • Nails have sharp pointed ends with a very small area
  • This concentrates the force, creating a large pressure over a small area
  • This allows the nail to be hammered into a wall

• This equation for pressure tells us that
  • if a force is spread over a large area it will result in a small pressure
  • if it is spread over a small area it will result in a large pressure

The surface area of the shoe affects the pressure applied to the ground

High heels produce a higher pressure on the ground because of their smaller area, compared to flat shoes