AQA AS Level Physics Paper 2, June 2022: Question 23

1 mark · Easy difficulty · Multiple Choice

Identify the correct description and unit of a couple from a multiple-choice table.

Practise this question

Question

A multiple-choice question numbered 23 asking 'Which description of a couple and its unit is correct?'. Below is a table with four rows labeled A, B, C, and D, each containing a description and a unit: A states 'consists of two equal parallel forces' with unit N m^-1; B states 'produces translational motion' with unit N m; C states 'consists of two equal and opposite forces' with unit N m; D states 'produces rotational motion' with unit N m^-1.
Question text

23 Which description of a couple and its unit is correct?

[1 mark]

Description Unit

A consists of two equal parallel forces N m−1

B produces translational motion N m

C consists of two equal and opposite forces N m

D produces rotational motion N m−1

Mark scheme

Show the mark scheme The mark scheme indicates that the correct answer for question 23 is C, corresponding to the description 'consists of two equal and opposite forces' with the unit N m.

23 C (AO1) consists of two equal and opposite forces N m

How to answer it

Characteristics and Units of a Couple

What this question tests

This question assesses your foundational knowledge of rotational dynamics (AO1), specifically the definition of a mechanical couple, its directional properties, and its correct SI derived unit.

Question 2.3 • Multiple Choice • 1 Mark

Exam Breakdown

✅ Correct Answer: C

Description: Consists of two equal and opposite forces.
Unit: N m

Mark Awarded: 1 / 1 for selecting option C.

💡 Key Knowledge

  • A couple requires two equal-magnitude forces acting in opposite directions along parallel lines of action (not the same line).
  • A couple produces pure rotational motion with no resultant linear (translational) force.
  • The moment of a couple is calculated as: Force × perpendicular distance between the forces , giving the unit newton-metres ( N m ).

🧠 Exam Technique

  • Process of elimination: Check the unit first. Since a couple measures a moment ( Force × distance ), the unit must be N m . This instantly rules out options A and D.
  • Between remaining options B and C, remember that translational motion means linear movement, which a balanced couple does not produce.

❌ Common Errors

  • Confusing a couple with a single moment or spring constant units ( N m⁻¹ ).
  • Forgetting that the two forces making up a couple must be strictly opposite in direction, not just parallel.

Topics

Physics · 3.4 Mechanics and materials

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.