Lesson R6

R6 Friction and limiting equilibrium Quiz: AQA Maths, Unit 12

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson R6, Friction and limiting 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. The friction model F <= mu R means:

    • Friction does not depend on the normal reaction
    • Friction is always greater than the normal reaction
    • Friction can be at most mu times the normal reaction
    • Friction is always mu times the weight

  2. The coefficient of friction is:

    • The product of friction and the normal reaction
    • The ratio of weight to friction
    • The ratio of limiting friction to the normal reaction
    • The friction force per unit mass

  3. Limiting friction occurs when:

    • The body is at rest with no forces acting
    • Friction is greater than the applied force
    • The body is on the point of sliding and F = mu R
    • The friction force is zero

  4. A body on a horizontal surface has no other vertical forces. What is the normal reaction R?

    • 2mg
    • F
    • Zero
    • mg

  5. In which direction does friction act on a body?

    • In the direction of the applied force always
    • In the direction of gravity
    • Opposite to the direction of actual or intended relative motion
    • Perpendicular to the surface

  6. A 5 kg block rests on a rough horizontal floor with mu = 0.4, and g = 10 m s^-2. What is the limiting friction?

    • 0.4 N
    • 50 N
    • 20 N
    • 125 N

  7. A 10 kg crate on a rough floor with mu = 0.3 is pulled horizontally by 20 N from rest, with g = 10 m s^-2. What happens?

    • Friction is zero and the crate stays at rest
    • Friction is 20 N and the crate moves
    • Friction is 20 N and the crate stays at rest
    • Friction is 30 N and the crate moves

  8. The same crate (10 kg, mu = 0.3, g = 10 m s^-2) is pulled horizontally by 40 N. What is its acceleration?

    • 0 m s^-2
    • 3 m s^-2
    • 4 m s^-2
    • 1 m s^-2

  9. A 4 kg body rests on a rough plane inclined at 30 degrees, with g = 10 m s^-2. What is the normal reaction?

    • 34.6 N
    • 40.0 N
    • 23.1 N
    • 20.0 N

  10. A 40 N block rests on a rough slope, with a tangential component of weight 20 N down the slope and maximum friction 12 N. What happens?

    • It stays in equilibrium because friction exceeds weight
    • It stays at rest, since 12 N exceeds 20 N
    • It slides, since 20 N exceeds the limiting friction of 12 N
    • It stays at rest, since friction of 20 N holds it

  11. A body is on the point of sliding down a rough plane. Which relationship holds for the angle theta of the plane?

    • sin(theta) = mu
    • cos(theta) = mu
    • tan(theta) = mu
    • mu = theta

  12. A 5 kg block on a rough horizontal plane with mu = 0.2 is pulled by 15 N at 30 degrees above the horizontal, with g = 10 m s^-2. What is the friction force, to 1 decimal place?

    • 3.0 N
    • 10.0 N
    • 8.5 N
    • 4.0 N

  13. For the block in the previous question (5 kg, mu = 0.2, pulled by 15 N at 30 degrees, g = 10 m s^-2), what is the acceleration, to 2 decimal places?

    • 0.20 m s^-2
    • 1.50 m s^-2
    • 0.90 m s^-2
    • 2.60 m s^-2

  14. A 6 kg body slides at constant velocity on a rough horizontal surface with mu = 0.25, with g = 10 m s^-2. What horizontal force is applied?

    • 15 N
    • 60 N
    • 6 N
    • 24 N

  15. A 4 kg body slides down a rough plane inclined at 30 degrees with mu = 0.2, g = 10 m s^-2. What is its acceleration, to 1 decimal place?

    • 5.0 m s^-2
    • 3.3 m s^-2
    • 4.3 m s^-2
    • 1.7 m s^-2

  16. A body rests in equilibrium on a rough plane with mu = 0.6. What is the largest angle with the horizontal before it slips, to 1 decimal place?

    • 59.0 degrees
    • 16.7 degrees
    • 45.0 degrees
    • 31.0 degrees

  17. A body on the point of sliding has friction 12 N and normal reaction 30 N. What is the coefficient of friction?

    • 0.25
    • 0.6
    • 2.5
    • 0.4

  18. A 5 kg block on a rough table with mu = 0.2 is connected by a light string over a smooth pulley to a hanging 3 kg mass, with g = 10 m s^-2. What is the acceleration?

    • 1.5 m s^-2
    • 0.25 m s^-2
    • 3.0 m s^-2
    • 2.5 m s^-2

  19. For the system in the previous question (5 kg block with mu = 0.2 and 3 kg hanging, g = 10 m s^-2), what is the tension in the string?

    • 22.5 N
    • 7.5 N
    • 15 N
    • 30 N

  20. A body of weight 10 N rests on a rough horizontal surface with mu = 0.3. A horizontal force of 2 N is applied. Which statement is correct?

    • It slides, since friction is zero
    • It is in equilibrium, with friction of 2 N since 2 N is less than the limiting value 3 N
    • It is in equilibrium, with friction of 3 N
    • It slides, since 2 N is less than its weight

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