Pressure
Pressure is force per unit area.
About this topic
Pressure is the force acting per unit area, P = F/A, measured in pascals (1 Pa = 1 N/m²). The same force on a smaller area gives greater pressure, which is why knives are sharp and snowshoes are wide.
Pressure acts on surfaces perpendicular to them, in fluids in all directions. Atmospheric pressure is about 101,000 Pa, and in a liquid, pressure increases with depth: P = ρgh. Every 10 m of water adds about one atmosphere. In a hydraulic system, pressure is transmitted equally, so a small force on a small piston produces a large force on a large piston.
Example: a 60 kg person standing on both feet of area 0.04 m² exerts about 14,700 Pa, but on high heels with a tiny area the pressure can exceed that of an elephant. Divers feel pressure in their ears, car jacks and brakes use hydraulics, and drawing liquid with a straw uses pressure differences.
Misconception: pressure and force are not the same; a large force can produce a small pressure if spread over a large area. Also, water pressure depends on depth, not on the shape or width of the container.
Key ideas
- P = F/A
- Unit: pascal
- Sharp knives have small area, big pressure
Quick check
Use cases: where Pressure helps
- Homework: review the key idea behind Pressure before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Pressure without notes.
- Visual learning: play with the interactive lab to see how Pressure changes when you adjust its inputs.
- Teaching a friend: explain Pressure in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Pressure?
Pressure is force per unit area.
What will I learn in Pressure?
P = F/A. Unit: pascal. Sharp knives have small area, big pressure.
Is Pressure part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Pressure lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Pressure?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.