Lesson R4

R4 Newton's third law and equilibrium Quiz: AQA Maths, Unit 12

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson R4, Newton's third law and equilibrium: 20 multiple choice questions for the AQA Maths (7357), Unit 12: Mechanics, written with Revision Ninja.

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The 20 questions

  1. Newton's third law states that if body A exerts a force on body B, then:

    • B exerts a force on A only when they touch
    • B exerts an equal and opposite force on A
    • The forces on A always balance
    • B exerts a smaller force on A

  2. The two forces in a Newton's third law pair act on:

    • The same body
    • Different bodies
    • Bodies at right angles only
    • The same body in opposite directions so they balance

  3. A book rests on a table. Are its weight and the normal reaction from the table a Newton's third law pair?

    • Yes, because they are a Newton's third law pair
    • Yes, because they act on different bodies
    • No; they act on the same body and are equal and opposite
    • Neither force acts on the book

  4. A particle is in equilibrium. Which statement is correct?

    • All forces acting on it must be equal
    • The resultant force on the particle is zero
    • The particle has no weight
    • The particle must be at rest

  5. A light string passes over a smooth pulley with masses on each side. What is true of the tension on the two sides?

    • It is zero
    • It is equal on both sides
    • It is twice the weight on each side
    • It is greater on the side with the heavier mass

  6. Particles A (3 kg) and B (2 kg) are connected by a light inextensible string over a smooth pulley, with A hanging. With g = 10 m s^-2, what is the acceleration?

    • 2 m s^-2
    • 0.2 m s^-2
    • 5 m s^-2
    • 10 m s^-2

  7. For the system in the previous question (A 3 kg, B 2 kg, g = 10 m s^-2), what is the tension in the string?

    • 30 N
    • 24 N
    • 12 N
    • 20 N

  8. A particle is in equilibrium under forces 10 N west, 6 N north and a third force F. What is the magnitude of F, to 1 decimal place?

    • 8.0 N
    • 4.0 N
    • 11.7 N
    • 16.0 N

  9. Forces of 6 N and 8 N act at right angles on a particle in equilibrium with a third force. What is the magnitude of the third force?

    • 8 N
    • 14 N
    • 10 N
    • 2 N

  10. For a particle in equilibrium under coplanar forces, what is the sum of the components of the forces in any one direction?

    • Equal to the largest force
    • Positive
    • Zero
    • Equal to the weight

  11. A 20 N force acts at 60 degrees above the horizontal. What is its vertical component, to 1 decimal place?

    • 10.0 N
    • 17.3 N
    • 20.0 N
    • 34.6 N

  12. A particle of weight 40 N on a horizontal table is pulled by a string at 30 degrees above the horizontal with tension 10 N. What is the normal reaction from the table?

    • 35 N
    • 45 N
    • 40 N
    • 30 N

  13. Masses of 5 kg and 3 kg are connected by a light string over a smooth pulley and released, with g = 10 m s^-2. What is the acceleration?

    • 5 m s^-2
    • 2.5 m s^-2
    • 2 m s^-2
    • 0.25 m s^-2

  14. A 4 kg particle A on a smooth horizontal table is connected by a light string to a 2 kg particle B on the same table. A horizontal force of 12 N pulls A away from B. What is the tension in the string?

    • 8 N
    • 4 N
    • 12 N
    • 2 N

  15. A person pushes against a wall with a force of 200 N. What force does the wall exert on the person?

    • Zero
    • 200 N, directed away from the wall
    • 200 N, directed towards the wall
    • 100 N, directed away from the wall

  16. A particle is in equilibrium under forces (2i + j) N, (-i + 3j) N and F. What is F?

    • 3i + 4j N
    • i + 4j N
    • -3i - 4j N
    • -i - 4j N

  17. A light inextensible string passes over a smooth pulley, connecting a 4 kg particle on a smooth horizontal table to a hanging 6 kg particle. With g = 10 m s^-2, what is the acceleration?

    • 2.4 m s^-2
    • 10 m s^-2
    • 4 m s^-2
    • 6 m s^-2

  18. For the system in the previous question (4 kg on a smooth table, 6 kg hanging, g = 10 m s^-2), what is the tension?

    • 24 N
    • 16 N
    • 40 N
    • 60 N

  19. Three coplanar forces keep a particle in equilibrium. If they are drawn tip to tail, what shape do they form?

    • An open chain
    • A closed triangle
    • Three lines meeting at one point
    • A square

  20. Two particles of masses 6 kg and 4 kg are connected by a light string over a smooth pulley, with the 6 kg hanging. With g = 10 m s^-2, what is the tension?

    • 40 N
    • 48 N
    • 24 N
    • 60 N

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