Pressure
- Pressure tells us how concentrated a force is, it is defined as the force per unit area
- This equation shows:
- 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
Different pressure is exerted for the same force on different areas
- The units of pressure depend on the units of area:
- If the area is measured in cm2 (and the force in N), then the pressure will be in N/cm2
- If the area is measured in m2 (and the force in N), then the pressure will be in N/m2
- Pressure can also be measured in pascals, Pa where 1 Pa is the same as 1 N/m2
- Pressure, unlike force, is a scalar quantity
- Therefore pressure does not have a specific direction
Worked example
A cylinder is placed on a horizontal surface as shown below
The mass of the cylinder is 4.7 kg and the diameter is 8.4 cm.Calculate the pressure produced by the cylinder on the surface in Pa.
Examiner Tip
The area referred to is the ‘cross-sectional’ area of a 3D object. This is the area of the base that the force is applied on. For a cylinder, this will be a circle.
