A-LevelMathematicsMechanics9709/41 · May/June 2018 · Q24 Marks

The diagram shows three coplanar forces acting at the point O. The magnitudes of the forces are 6N, 8 N and 10 N. The angle between the 6 N force and the 8 N force is 90°. The forces are in equilibrium. Find the other angles between the forces.

The diagram shows three coplanar forces acting at the point O. The magnitudes of the forces are 6N, 8 N and 10 N. The angle between the 6 N force and the 8 N force is 90°. The forces are in equilibrium. Find the other angles between the forces.[4]

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Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

[M1] Introduce α or β, an angle between the 10N force and the vertical or horizontal and attempt to resolve forces
[A1] α = 36.9 or β = 53.1
[B1] Angle between 6N and 10N is 126.9
[B1] Angle between 8N and 10N is 143.1
[M1] Attempt to use Lami's theorem γ (8 and 10), δ (6 and 10)
[A1] All correct
[B1] Angle between 8N and 10N is γ =143.1
[B1] Angle between 6N and 10N is δ =126.9

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