Pressure
Force per unit area.
Formula
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Example
A 100 N force on 0.5 m² gives P = 100/0.5 = 200 Pa.
How it works
Pressure tells you how concentrated a force is on a surface. The same force spread over a larger area produces less pressure, because each square metre has to carry less of the load. That is why sharp points can pierce materials more easily and why wide tyres or snowshoes reduce sinking. The unit of pressure is the pascal (Pa), which is equivalent to 1 newton per square metre.
When to use it
Use this formula whenever you need to find the pressure exerted by a force on a surface, such as in hydraulics, tyres, cutting tools, or standing on soft ground. It is also useful in basic mechanics and materials science for comparing how forces affect different areas.
Worked example, step by step
A crate presses down on the floor with a force of 250 N. The contact area is 2.5 m². Use P = F / A. P = 250 / 2.5 P = 100 Pa So the pressure on the floor is 100 pascals.
Common mistakes to avoid
- Using mass instead of force; pressure depends on force in newtons, not kilograms
- Forgetting to convert area to square metres before calculating
- Rearranging the formula incorrectly and dividing area by force instead of force by area
Did You Know?
A sharp knife cuts because the same force over a tiny edge produces enormous pressure.
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