A-LevelMathematicsMechanics9709/42 · Feb/Mar 2021 · Q35 Marks
A particle Q of mass 0.2 kg is held in equilibrium by two light inextensible strings PQ and QR. P is a fixed point on a vertical wall and R is a fixed point on a horizontal floor. The angles which strings PQ and QR make with the horizontal are 60° and 30° respectively (see diagram).
- Find the tensions in the two strings.[5]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2021). The mark or mark type is shown in brackets.
- [1] For attempting to resolve forces in either direction.
- [1] Tp cos 60 = TR cos 30
- [1] Tp sin 60 = TR Sin 30 + 0.2g
- [1] From 2 equations, with correct number of relevant terms.
- [1] Both correct. Allow Tp = 2√3 N.
- [1] Attempt one pair of Lami's equations. Correct angles.
- [1]
- [1]
- [1] From equations of the correct form.
- [1] Both correct. Allow Tp = 2√3 N
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