Mathematics 9709 · AS & A Level · Representation of data

Representation of data — practice question

A non-uniform rod $AB$ has weight $6\,\text{N}$ and is in limiting equilibrium, with end $A$ touching a rough vertical wall. $AB = 1.2\,\text{m}$, the centre of mass of the rod is $0.8\,\text{m}$ from $A$, and the angle between $AB$ and the downward vertical is $\theta^\circ$. At $B$, a force of magnitude $10\,\text{N}$ is applied at an angle of $30^\circ$ to the upwards vertical (see diagram). The rod and the line of action of the $10\,\text{N}$ force both lie in a vertical plane perpendicular to the wall.
(i)[4]

Find the numerical value of $\theta$.

(ii)[2]

Find the coefficient of friction for the wall contact of the rod.

Worked solution & mark scheme

This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: Forming a three-term equation that can be solved in $\sin\theta$ and $\cos\theta$, for example $10\cos30 \times 1.2\sin\theta - 10\sin30 \times 1.2\cos\theta = 6 \times 0.8\sin\theta$

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