A-LevelMathematicsMechanics9709/51 · May/June 2019 · Q67 Marks
ABC is a uniform lamina in the form of a triangle with AB = 0.3 m, BC = 0.6 m and a right angle at B [Figure 6.1].
- (i)State the distances of the centre of mass of the lamina from AB and from BC.[2]
- (ii)The lamina is freely suspended at B and hangs in equilibrium. Find the angle between AB and the horizontal.[2]
- (iii)A force of magnitude 12 N is applied along the edge AC of the lamina in the direction from A towards C. The lamina, still suspended at B, is now in equilibrium with AB vertical. Calculate the weight of the lamina.[3]
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Mark scheme
Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.
- [B1] From AB = 0.2
- [B1] From BC = 0.1
- [M1] θ is the angle between AB and the horizontal
- [A1] θ = 26.6°
- [M1A1] Take moments about B. (W is the weight of the lamina)
- [A1] W=16.1 N
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