Lesson 2.5.1

2.5.1 Moments, centre of gravity and the principle of moments Quiz: Pearson Edexcel Physics, Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 2.5.1, Moments, centre of gravity and the principle of moments: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 2: Mechanics, written with Revision Ninja.

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The 20 questions

  1. The moment of a force about a point is defined as:

    • The force divided by the distance from the point.
    • The force multiplied by the perpendicular distance from the point to the line of action of the force.
    • The force multiplied by the total distance moved.
    • The force multiplied by the square of the distance from the point.

  2. The principle of moments states that for a body in equilibrium:

    • The clockwise moments are always larger than the anticlockwise moments.
    • The moments about one point are zero, but about another point they are not.
    • The sum of all forces is larger than the sum of all moments.
    • The sum of the clockwise moments about a point equals the sum of the anticlockwise moments about the same point.

  3. The centre of gravity of a uniform rod is located:

    • At its geometric centre
    • At one end of the rod
    • At a point one third of the way along
    • At the end nearest the heaviest load

  4. The SI unit of moment of a force is:

    • N m^-1
    • N
    • J
    • N m

  5. A spanner of length 2.0 m is pushed at its end by a force of 40 N, perpendicular to the spanner. What is the moment about the nut?

    • 80 N m
    • 20 N m
    • 40 N m
    • 0.05 N m

  6. A force of 40 N acts on a 0.50 m lever at 30 degrees to the lever. What is the moment about the pivot at the end of the lever?

    • 35 N m
    • 10 N m
    • 20 N m
    • 17 N m

  7. A child of weight 300 N sits 1.5 m from the pivot of a seesaw. Where must an adult of weight 500 N sit on the other side to balance it?

    • 2.5 m from the pivot
    • 0.90 m from the pivot
    • 0.60 m from the pivot
    • 1.5 m from the pivot

  8. A uniform plank 4.0 m long weighs 200 N and is pivoted at its left end. Where does its weight act from the pivot?

    • 4.0 m from the pivot
    • 200 m from the pivot
    • 1.0 m from the pivot
    • 2.0 m from the pivot

  9. A uniform beam 4.0 m long and weighing 100 N rests on two supports at its ends. What is the reaction force at each support?

    • 200 N
    • 50 N
    • 100 N
    • 25 N

  10. A uniform beam 3.0 m long weighs 60 N and is pivoted at its left end. A 90 N load acts at 2.0 m from the pivot. A rope holds the right end vertically upwards. What is the tension in the rope?

    • 180 N
    • 150 N
    • 60 N
    • 90 N

  11. Why does using a longer spanner make a nut easier to loosen?

    • A longer spanner reduces the weight of the nut.
    • A longer spanner reduces the friction in the nut.
    • A longer spanner makes the force act at a smaller angle.
    • For the same force, a longer lever gives a larger moment about the nut.

  12. A 60 N m clockwise moment and a 25 N m anticlockwise moment act about the same pivot. What is the net moment?

    • 0 N m
    • 35 N m anticlockwise
    • 85 N m clockwise
    • 35 N m clockwise

  13. An object will topple over when:

    • The vertical line through its centre of gravity falls outside its base.
    • Its mass is greater than its height.
    • Its weight is larger than the force of friction.
    • Its centre of gravity is above the middle of its base.

  14. A non-uniform metre rule balances on a pivot at the 60 cm mark. Where is its centre of gravity?

    • At the 50 cm mark
    • At the 100 cm mark
    • At the 60 cm mark
    • At the 30 cm mark

  15. A 2.0 m long uniform rod of weight 20 N is pivoted at one end. It is held horizontally by a force at its free end acting vertically upwards. What is this force?

    • 5 N
    • 20 N
    • 10 N
    • 40 N

  16. A uniform plank rests on a fulcrum at its midpoint. Which change would make it topple towards the right side?

    • Adding a light load to the centre
    • Moving the fulcrum to the left
    • Removing a load from the right side
    • Moving a heavy load to the right of the fulcrum

  17. A 5.0 N force is applied perpendicular to a 0.20 m spanner. What is the moment about the bolt?

    • 0.25 N m
    • 1.0 N m
    • 10 N m
    • 4.0 N m

  18. A rope pulls a uniform 2.0 m beam, weighing 80 N, upwards at one end while the other end is on a pivot. What is the main reason the beam stays horizontal?

    • The rope tension equals the beam's weight with no moment.
    • The moment of the rope tension about the pivot balances the moment of the beam's weight.
    • The beam's weight acts at its free end.
    • The pivot provides a clockwise moment.

  19. A uniform 2.0 m plank of weight 50 N rests on two supports at its ends, with a 150 N load placed 0.50 m from the left end. What is the reaction force at the left support?

    • 100 N
    • 200 N
    • 62.5 N
    • 137.5 N

  20. Three non-parallel coplanar forces keep a body in equilibrium. What must be true of their lines of action?

    • They are all parallel to each other.
    • They all pass through the centre of gravity but never meet.
    • They meet at a single point.
    • They are all equal in magnitude.

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