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What is pressure?

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Quick answer

Pressure is the amount of force pushing on a given area. The same force concentrated on a small area creates high pressure (like a sharp knife), while spread over a large area it creates low pressure (like snowshoes). It is measured in pascals (Pa).

Key things to understand

  1. Pressure = force ÷ area. The smaller the area a force acts on, the higher the pressure.
  2. It's measured in pascals (Pa); other units include atmospheres (atm) and bars.
  3. Gases and liquids exert pressure in all directions — air pressure, water pressure, blood pressure.
  4. A sharp blade cuts well because its tiny edge area turns a modest force into very high pressure.

People also ask

Why is a sharp knife better than a blunt one?
A sharp edge has a tiny contact area, so the same force creates much higher pressure — enough to cut. A blunt edge spreads the force over more area, lowering the pressure.
What is atmospheric pressure?
The weight of the air above us pressing down. At sea level it's about 101,325 pascals (1 atmosphere), and it decreases as you go higher, where there's less air above.
How does pressure work in liquids?
Liquids push in all directions, and pressure increases with depth — which is why your ears feel more pressure the deeper you dive.

Part of the guide: Everyday Machines →