AQA GCSE Physics - 5.5 Pressure - 5.5.1 Pressure

Sep 5, 2026

Revision notes for AQA GCSE Physics topic 5.5 on pressure in fluids, focusing on what pressure is, how it acts in liquids and gases, and why smaller contact areas create larger pressure. Includes real-life examples such as drawing pins, tractors, and nails, plus explanation of forces exerted at right angles to surfaces when objects are immersed in fluids. Provides the pressure equation, unit of measurement, and a worked calculation example with unit guidance and significant-figure rounding.

LanguageEnglish

CategoryExam

FormatPDF

Pages20

Reading Time50 min

AccessFree to download

5.5 Pressure & Pressure Differences in Fluids

5.5.1 Pressure

5.5.2 Atmospheric Pressure

Head to www.savemyexams. com for more awesome resources AQA GCSE Physics 5 .5 Pressure & Pressure Diyerences in Fluids Contents 5.5.1 Pressure 5.5.2 Atmospheric Pressure 5.5.3 Pressure in a Liquid 5.5.4 Upthrust Page 1 of 20 © 2015 − 2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources 5.5.1 Pressure Pressure in a Fluid A }uid is either a liquid or a gas Pressure is de|ned as The concentration of a force orthe force per unit area For example, when a drawing pin is pushed downwards: It is pushed into the surface, rather than up towards the |nger This is because the sharp point is more concentrated (a small area) creating a larger pressure When you push a drawing pin, it goes into the surface (rather than your |nger) Example 1: Tractors Tractors have large tyres This spreads the weight (force) of the tractor over a large area This reduces the pressure which prevents the heavy tractor from sinking into the mud Example 2: Nails Nails have sharp pointed ends with avery small area This concentrates the force, creating a large pressure over a small area This allows the nail to be hammered into a wall When an object is immersed in a liquid, the liquid will exert pressure, squeezing the object Page 2 of 20 © 2015 − 2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources The pressure exerted on objects in }uids creates forces against surfaces These forces act at 90 degrees (at right angles) to the surface The pressure of a }uidonan object creates a force normal (at right angles) to the surface Page 3 of 20 © 2015 − 2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources Calculating Pressure The pressure atthe surface of a }uid can be calculated using the equation: Pressure is measured in the units Pascals (Pa) The area should always bethe cross-sectional area of the object This means the area where the force is at right angles to it This equation can be rearranged with the help of a formula triangle: Page 4 of 20 © 2015 − 2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources This equation means: If a force is spread over a large area it will result in a small pressure If it is spread over a small area itwill result in a large pressure Page 5 of 20 © 2015 − 2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources High heels produce a higher pressure on the ground because of their smaller area, compared to }at shoes Page 6 of 20 © 2015 − 2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources Worked example The diagram below shows the parts of the lifting machine used to move the platform up and down. The pump creates pressure in the liquid of 5 .28 × 105 Pato move the platform upwards. Calculate the force that the liquid applies to the piston. Step 1: List the known quantities Cross-sectional area = 2 .73 × 10-2 m2 Pressure = 5 .28 × 105 Pa Step 2: Write down the relevant equation Step 3: Rearrange for the force, F F = p × A Step 4: Substitute the values into the equation Page 7 of 20 © 2015 − 2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources F = (5 .28 × 105) × (2 .73 × 10-2) = 14 414 .4 Step 5: Round to the appropriate number of signi|cant |guresand quote the correct unit F = 14 400 N = 14 .4 kN (3 s.f ) Examiner Tip Look out for the units for the force!Large press

FAQs

What does pressure mean in the context of fluids?

Pressure is defined as the force per unit area. In fluids, that pressure acts on surfaces and can create forces.

Why does a drawing pin produce a larger pressure when pushed down?

The sharp point has a very small area, so the same force is concentrated over a smaller area, creating larger pressure.

How is pressure calculated and measured?

Pressure can be calculated using Pressure = force ÷ area (F = p × A when rearranged). Pressure is measured in Pascals (Pa).

Sep 5, 2026

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