What is Pressure?
Pressure describes how concentrated a force is over a surface — the same force spread over a small area creates far more pressure than over a large area. It's why a sharp knife cuts easily but a flat hand doesn't.
Pressure is force per unit area: P = F/A, measured in pascals (Pa) where 1 Pa = 1 N/m². For the same force, a smaller area produces greater pressure.
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Step-by-step worked examples
A 600 N force is applied over an area of 0.3 m². Find the pressure.
P = F/A = 600/0.3 = 2000 Pa
A knife blade has a contact area of 0.0002 m² and you press with 20 N. Find the pressure.
P = F/A = 20/0.0002 = 100000 Pa
A pressure of 250 Pa acts over an area of 4 m². Find the force.
F = P × A = 250 × 4 = 1000 N
Flashcards
Quick quiz
Q1.A 100 N force acts on a 0.5 m² area. The pressure is...
Q2.Why do snowshoes prevent sinking into snow?
Q3.The SI unit of pressure is the...
Q4.A force of 900 N acts over 3 m². What is the pressure?
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Common mistakes
Pressure and force are the same thing. — Correct: Force is a push/pull; pressure is force spread over an area — the same force gives different pressure on different areas.
A bigger area always means more pressure. — Correct: For a fixed force, a bigger area means LESS pressure, not more.
Pressure has no units, it's just a ratio. — Correct: Pressure has the unit pascal (Pa), equal to N/m².
You need a huge force to get high pressure. — Correct: A small force over a tiny area (like a needle tip) creates very high pressure.
FAQ
What is pressure?
Pressure is force applied per unit area, P = F/A, measured in pascals (Pa).
What is the pressure formula?
P = F/A, where F is force in newtons and A is area in square meters.
What are examples of pressure?
A sharp knife cutting easily, snowshoes preventing sinking, and atmospheric pressure pushing on your body.
How to calculate pressure?
Divide the applied force by the area it acts on: P = F ÷ A.