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Pearson Edexcel International GCSE (9–1) · PHYSICS · Section

THE TURNING EFFECT OF FORCES

24 practice questions

Start practising (24 questions)

Practice questions

21–24 of 24

  1. Question 21

    3 marks · Normal

    A bridge is supported at both ends. A heavy truck stops near the left end of the bridge. Explain, using the principle of moments, how the upward forces at the left and right supports change as the truck moves from the left end to the centre of the bridge.

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  2. Question 22

    6 marks · Hard

    A uniform metal plank of length 2.5 m and mass 4.0 kg is placed horizontally across a small stream, resting on rocks at each end (points R and S). A stone of mass 2.0 kg is placed 0.75 m from end R, as shown.

    Geometry diagram with points R, S, A, Centre of gravityStone (2.0 kg)Support RSupport SRSCentre of gravity
    Plank and stone over stream

    Take gravitational field strength . Ignore the weight of the plank unless stated otherwise.

    (a)

    Calculate the upward force at support S when only the stone is on the plank. (Ignore the weight of the plank.)

    [3 marks]
    (b)

    Now include the weight of the plank. Calculate the new upward force at support S.

    [3 marks]
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  3. Question 23

    5 marks · Hard

    A carpenter tries to lift a heavy lid off a crate using a crowbar. The crowbar is 1.2 m long. She places the fulcrum (pivot point) 0.2 m from one end. She applies a vertical downward force of 250 N at the far end of the bar (opposite the pivot).

    (a)

    Calculate the moment produced by the carpenter's force about the fulcrum.

    [2 marks]
    (b)

    If the lid is just lifted (i.e., the system is in balance), calculate the minimum upward force at the lid end needed to balance the moment.

    [3 marks]
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  4. Question 24

    5 marks · Hard

    An athlete is balancing on a horizontal board that is supported at both ends (points L and M). The board has negligible mass. The athlete stands a distance d from support L on the 3.0 m long board. The athlete's weight is 630 N.

    (a)

    Write an expression for the upward force, F_M, at support M in terms of d.

    [2 marks]
    (b)

    The athlete stands 2.2 m from support L. Calculate the upward force at support M.

    [3 marks]
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