A mechanic uses a spanner to tighten a bolt. When the mechanic cannot tighten the bolt any further using a short spanner, they switch to a longer spanner. Explain why the longer spanner makes it easier to tighten the bolt further, using the idea of moments.

AQA GCSE Physics (8463) — 4.5.4 Moments, levers and gears (Phys only) · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

A moment is the turning effect of a force about a pivot.
The bolt acts as the pivot point.
Moment = force × perpendicular distance from the pivot.
The longer spanner increases the perpendicular distance, so a greater moment is produced for the same applied force.

Examiner tips

  • Use the definition of a moment first. Show the formula and identify the pivot. Explain how the distance changes. Keep the answer concise and use the exact wording from the mark scheme.

Common mistakes

  • Confusing the force with the moment. Forgetting to mention the bolt as the pivot. Using the wrong variable for distance (e.g., using the whole length instead of the perpendicular distance).

Mark scheme (4 marks)

  1. A moment is the turning effect of a force about a pivot
  2. The bolt acts as the pivot point
  3. Moment = force × perpendicular distance from the pivot
  4. The longer spanner increases the perpendicular distance, so a greater moment is produced for the same applied force

Key terms in this question

moment

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