GCSE Physics resources

AQA GCSE Forces

Moments, Levers and Pressure

A moment is the turning effect of a force about a pivot and uses perpendicular distance. Pressure is force per unit area, so the same force can produce different pressures when the contact area changes.

AQA 8463 GCSE Physics FoundationHigher

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The revision snapshot

A moment is the turning effect of a force about a pivot and uses perpendicular distance. Pressure is force per unit area, so the same force can produce different pressures when the contact area changes.

By the end, you should be able to:

  • Use turning effect and force per area.
  • Apply the forces model, evidence or method to an unfamiliar exam context.
  • Recognise and correct this wrong turn: Using distance along the lever instead of perpendicular distance.

Before you revise

Diagnostic question

Choose an answer from memory. Your result tells you what to watch for in the guide.

Which statement correctly summarises moments, levers and pressure?

Core revision guide

Learn the model, then use it

Moments, Levers and Pressure questions become manageable when the central model, evidence and exam method are kept together. Read the explanation, test the misconception and then apply the idea without looking back.

Use turning effect and force per area

A moment is the turning effect of a force about a pivot and uses perpendicular distance. Pressure is force per unit area, so the same force can produce different pressures when the contact area changes.

Build the physics picture

A moment depends on perpendicular distance from the pivot, so moving the same force further out increases its turning effect. Pressure is force divided by area: a sharp heel or knife concentrates a force on a small area, whereas a wide snowshoe reduces pressure.

Relationships used in this guide

Moment: moment = force × perpendicular distance (N m, N, m). Pressure: p = F ÷ A (Pa, N, m²). Choose each relationship from the physical change described, convert quantities into compatible units and keep the unit beside the final answer.

A lever shows perpendicular distance from a pivot and a second panel compares the same force over large and small areas.
Use perpendicular distance for moments and area in square metres for pressure.Open the full-size exam diagram
Momentmoment = force × perpendicular distanceN m, N, m
Pressurep = F ÷ APa, N, m²

Misconception clinic

Replace the tempting answer

Read each belief, say what is wrong with it, then compare your correction.

Tempting idea: Using distance along the lever instead of perpendicular distance.

Use instead: A moment is the turning effect of a force about a pivot and uses perpendicular distance. Pressure is force per unit area, so the same force can produce different pressures when the contact area changes.

Tempting idea: Using area in cm² with Pa.

Use instead: A moment depends on perpendicular distance from the pivot, so moving the same force further out increases its turning effect. Pressure is force divided by area: a sharp heel or knife concentrates a force on a small area, whereas a wide snowshoe reduces pressure.

Tempting idea: Mixing moment and force.

Use instead: Mark the pivot or contact area, select the correct perpendicular distance or area and keep N, m and Pa units consistent.

Retrieval practice

Quick checks

1. Which exam method is most reliable for moments, levers and pressure?

2. Which statement correctly applies moments, levers and pressure to a question?

3. A pupil writes: “Using distance along the lever instead of perpendicular distance.” Which replacement is accurate?

Worked examples

See the method being built

These examples expose the difference between a secure use turning effect and force per area method and the common error “Using distance along the lever instead of perpendicular distance.”.

Example 1 · Calculate moment

A 30 N force acts perpendicularly 0.40 m from a pivot. Find moment.

  1. Use moment = force × distance.
  2. Calculate 30 × 0.40.
  3. Give N m.
Show the answer

Moment = 12 N m.

Example 2 · Balance a beam

A 10 N weight is 0.30 m from a pivot. What force at 0.15 m balances it?

  1. Equate clockwise and anticlockwise moments.
  2. 10 × 0.30 = F × 0.15.
  3. Rearrange.
Show the answer

F = 20 N.

Example 3 · Calculate pressure

A 600 N person stands on 0.030 m². Find pressure.

  1. Use p = F/A.
  2. Calculate 600 ÷ 0.030.
  3. Give pascals.
Show the answer

p = 20 000 Pa.

Exam precision

Exam technique: Use turning effect and force per area

Do this: Mark the pivot or contact area, select the correct perpendicular distance or area and keep N, m and Pa units consistent.

Independent practice

Exam-style questions

Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.

1. State the SI unit of moment.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: N m.

2. State the SI unit of pressure.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Pa (N/m²).

3. Explain why a longer spanner makes a nut easier to turn.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.

Model answer: It increases perpendicular distance, so the same force produces a larger moment.

4. A 100 N force acts 0.20 m from a pivot. Calculate moment.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award one mark for the correct relationship, one for a valid substitution and one for the final answer with its unit.

Model answer: 20 N m.

5. Explain why snowshoes reduce pressure.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.

Model answer: They spread the same force over a larger area.

6. State why distance must be perpendicular in a moment calculation.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Only the perpendicular separation produces the turning effect.

Questions pupils ask

Moments, Levers and Pressure FAQs

What is the main idea in Moments, Levers and Pressure?

A moment is the turning effect of a force about a pivot and uses perpendicular distance. Pressure is force per unit area, so the same force can produce different pressures when the contact area changes.

What mistake should I avoid in Moments, Levers and Pressure?

Using distance along the lever instead of perpendicular distance. A moment depends on perpendicular distance from the pivot, so moving the same force further out increases its turning effect. Pressure is force divided by area: a sharp heel or knife concentrates a force on a small area, whereas a wide snowshoe reduces pressure.

Useful next steps

Connect this guide to your next task

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