THE TURNING EFFECT OF FORCES
2 marks · EasyLook at the diagram below.
A beam 2.0 m long is supported at ends P and Q. A 400 N boy stands 0.5 m from Q.
(a)[2 marks]
How much of the boy's weight is supported by Q?
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 100 N
Must show: diagram showing beam, positions labelled
Common mistakes: Incorrectly dividing the weight equally
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly applies moments about P or formula for upward force on Q.
A1 (a) · 1 mark · Obtains correct value (100 N for Q).
Worked solution
Distance from Q to boy: 0.5 m.
Force supported by Q = (distance from P to boy) / (length) × boy's weight = (1.5/2.0) × 400 = 300 N by P, so Q supports 100 N.