Calculating Pressure in a Liquid
Higher Tier Only
- The pressure due to a column of liquid can be calculated using the equation
p = h × ρ × g
- Where:
- p = pressure in pascals (Pa)
- h = height of the column in metres (m)
- ρ = density of the liquid in kilograms per metre cubed (kg/m3)
- g = gravitational field strength on Earth in newtons per kilogram (N/kg)
- The force from the pressure is exerted evenly across the whole surface of an object in a liquid, and in all directions
The force from the pressure of objects in a liquid is exerted evenly across its whole surface
- The pressure is more accurately the difference in pressure at different depths h in a liquid, since the pressure changes with the depth
Worked example
Calculate the depth of water in a swimming pool where a pressure of 20 kPa is exerted.
The density of water is 1000 kg/m3 and the gravitational field strength on Earth is 9.8 N/kg.
Examiner Tip
This pressure equation will be given on your formula sheet, however, make sure you are comfortable with rearranging it for the variable required in the question!
