Define pressure as force per unit area; recall and use the equation p = F / A

What is Pressure?

Pressure is the amount of force applied per unit area. Think of it like the way you feel when you press your hand against a table – the harder you press, the higher the pressure.

Mathematically:

\$p = \frac{F}{A}\$

where \$F\$ is the force in newtons (N) and \$A\$ is the area in square metres (m²).

The SI unit of pressure is the pascal (Pa), where 1 Pa = 1 N m⁻².

Real‑World Analogy

Imagine you’re pushing a pizza box. If you press with the same force but spread it over a larger area (like using a flat hand), the pressure felt by the box is lower than if you press with a small, sharp tip. This is why a needle can puncture a balloon but a broad hand cannot.

📏 Tip: The smaller the area, the higher the pressure for the same force.

Example Calculation

Notice how halving the force but increasing the area reduces the pressure dramatically.

Exam Tips 🎓

1. Always write the formula \$p = \dfrac{F}{A}\$ before starting a calculation.
2. Check units: convert force to newtons and area to square metres before plugging into the formula.
3. Remember that pressure is a scalar; it has magnitude but no direction.
4. Use the symbol \$p\$ for pressure, \$F\$ for force, and \$A\$ for area.
5. When dealing with liquids, pressure increases with depth: \$p = \rho g h\$ (where ρ is density, g is gravity, h is depth).