Pressure
Pressure is the force acting per unit area, so the same force on a smaller area gives greater pressure.
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Pressure is the force acting per unit area, so the same force on a smaller area gives greater pressure.
- Pressure equals force over area
- Measured in pascals
- Sharp knives work because the area is small
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Pressure?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Pressure. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Pressure in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Pressure explains how the physical world behaves, from sport and transport to electricity and medicine.
Pressure in detail
Pressure is the force acting per unit area, p = F/A, measured in pascals (Pa), where 1 Pa = 1 N/m². The same force gives a larger pressure on a smaller area, which is why a sharp knife cuts better and why snowshoes spread weight to avoid sinking.
Pressure acts at right angles to a surface. Increasing the area reduces pressure, as with wide tractor tyres, while reducing the area increases it, as with nails and needles. Pressure calculations also apply to hydraulic systems and to gases, where particle collisions with the walls cause pressure.
How the interactive helps you understand Pressure
Watch the gas particle model in the interactive. Use any sliders or buttons it offers to change the values and see how the gas particle model responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Pressure.
Real-life uses and examples
- Explain everyday devices, such as brakes, lifts or chargers, using Pressure.
- Use Pressure to make sense of a practical and its results.
- Answer “explain” questions by linking Pressure to a clear cause and effect.
Common mistakes to avoid
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Mixing up Pressure with a related quantity that has different units.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Pressure
What is Pressure?
Pressure is the force acting per unit area, so the same force on a smaller area gives greater pressure.
What are the most important points about Pressure?
The main points are: Pressure equals force over area; Measured in pascals; Sharp knives work because the area is small.
Why is Pressure useful?
Understanding Pressure explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Pressure?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Pressure?
Related topics in Physics include Upthrust and Floating, Gravitational Potential Energy, Power.