Example 1: Finding Pressure (P = F/A)
Calculate the pressure exerted on the floor.
Write the formula: P = F / A
Substitute: P = 600 / 0.030
Answer: P = 20,000 Pa
Example 2: Finding Force (F = P × A)
Calculate the force exerted by the air on the window.
Write the formula: F = P × A
Substitute: F = 101,000 × 2.0
Answer: F = 202,000 N (about 202 kN — this is why windows must be strong!)
Example 3: Pressure in a Liquid — P = hρg (Higher Tier)
Calculate the pressure due to the seawater at that depth.
Write the formula: P = hρg
Substitute: P = 20 × 1025 × 9.8
Answer: P = 200,900 Pa ≈ 201 kPa
Note: total pressure on the diver also includes atmospheric pressure (101 kPa) on top.
Quick Check: Explain why a sharp knife cuts more easily than a blunt knife, even when the same force is applied.
A sharp knife has a much smaller cutting edge area. Using P = F/A, for the same force, a smaller area produces a much greater pressure. The higher pressure is more effective at cutting through the material.
This worked example covers Worked Examples within Pressure for GCSE Physics. Revise Pressure in Forces for GCSE Physics with 15 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 10 of 16 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Practice questions for Pressure
What is the correct equation for pressure?
Explain why a sharp knife cuts through food more easily than a blunt knife, even when the same force is applied to both.