AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Pressure in a fluid 1: area, A, in metres squared
Area, A, is the size of a surface measured in square metres (m²).
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 8 of 9
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Area, A, is the size of a surface measured in square metres (m²). In pressure calculations, A is the area of the surface that the force acts on at right angles. For a rectangular surface, multiply length by width, both in metres, so a 2 m by 3 m face has A = 6 m². For a circular piston, use A = πr², converting the radius to metres first. If a measurement is in cm, convert by dividing by 100 before squaring; for example, 50 cm = 0.50 m, so 0.50² = 0.25 m². Area is not the same as volume: volume uses m³. Always match the area to the surface actually in contact with the fluid or force.
What earns the marks
- State that area is measured in square metres (m²), not metres or cubic metres.
- Calculate the area of a rectangle by multiplying its length in metres by its width in metres.
- Calculate the area of a circle using A = πr², with the radius converted to metres before squaring.
- Convert centimetres to metres by dividing by 100, and convert cm² to m² by dividing by 10 000.
- Select the area of the surface in contact with the force or fluid, not the total surface area of the object.
- Substitute the area into pressure or force equations with consistent SI units.
Common mistakes and how to put them right
Using the diameter instead of the radius in A = πr².
Put it right by halving the diameter before squaring.
Forgetting to square the unit conversion, so 50 cm² is treated as 0.50 m².
Put it right by dividing by 10 000 to obtain 0.0050 m².
Using the total surface area of a block when only one face is in contact with the fluid.
Put it right by identifying the contact face and using its area only.
Exam tips
- Write the unit m² every time you state an area, and check that the unit matches the calculation.
- Convert all lengths to metres before calculating area, then square the conversion factor if the original unit was cm².
- In pressure questions, underline the word area and identify which surface the force acts on before substituting values.
Try the lesson
The start of the Pressure in a fluid 1: area, A, in metres squared lesson, made from checked teaching notes for this specification point.
Have a go first
A flat metal plate has an area of 4 m². What is this area in square centimetres?
Listen
Area, A, is the size of a surface measured in square metres (m²). In pressure calculations, A is the area of the surface that the force acts on at right angles. For a rectangular surface, multiply length by width, both in metres, so a 2 m by 3 m face has A = 6 m². For a circular piston, use A = πr², converting the radius to metres first. If a measurement is in cm, convert by dividing by 100 before squaring; for example, 50 cm = 0.50 m, so 0.50² = 0.25 m². Area is not the same as volume: volume uses m³. Always match the area to the surface actually in contact with the fluid or force. A strong answer earns marks for these points. State that area is measured in square metres (m²), not metres or cubic metres. Calculate the area of a rectangle by multiplying its length in metres by its width in metres. Calculate the area of a circle using A = πr², with the radius converted to metres before squaring. Convert centimetres to metres by dividing by 100, and convert cm² to m² by dividing by 10 000. A common slip: Using the diameter instead of the radius in A = πr². Instead, halving the diameter before squaring. Exam tip: Write the unit m² every time you state an area, and check that the unit matches the calculation.
Key words
Say what each word means before you turn the card.
Area
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Area of a rectangle
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Area of a circle
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Area in contact
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See every definition
- Area
- The size of a surface, measured in square metres (m²), not metres or cubic metres.
- Area of a rectangle
- Found by multiplying its length in metres by its width in metres.
- Area of a circle
- Calculated using A = πr², with the radius converted to metres before squaring.
- Area in contact
- The area of the surface actually in contact with the fluid or force, not the total surface area of the object.
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