| English | Pressure |
|---|---|
| Bahasa Melayu | Tekanan |
| 中文 | 压强 |
Definition
The force acting normally (perpendicularly) on unit area of a surface (pressure = force ÷ area); measured in pascals (Pa).
In exam terms
Pressure is the force acting normally (perpendicularly) on unit area of a surface. It is a scalar quantity with the symbol P and the SI unit pascal (Pa), where 1 Pa = 1 N m⁻².
The defining relationship is P = F ÷ A, where F is the perpendicular force in newtons (N) and A is the area in square metres (m²). For example, a force of 20 N spread over an area of 0.5 m² gives P = 20 N ÷ 0.5 m² = 40 Pa.
This is why a sharp knife (small area) cuts more easily than a blunt one for the same force, and why a tractor with wide tyres (large area) exerts less pressure on soft ground.
Do not confuse it with force
Do not confuse pressure with force. Force is the push or pull itself, measured in newtons (N), while pressure is force spread over an area, measured in pascals (Pa).
The same force gives a high pressure over a small area and a low pressure over a large area, so a nail tip pierces wood while the flat hammer head does not.
In Paper 2 this is usually asked as define pressure (state force per unit area acting normally) or calculate the pressure using P = F ÷ A. Watch the units: area must be in m² for the answer to come out in pascals.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)