Fig. 2.1 shows a sign spanning a road. The diagram labels the support post, concrete block, sign, horizontal distances of $1.8\,\text{m}$, $1.3\,\text{m}$ and $70\,\text{cm}$, point $P$, and a downward force labelled $W$. The sign has a mass of $3.4 \times 10^3\,\text{kg}$.
(a)[2]
Calculate the sign's weight $W$.
(b(i))[3]
Calculate the moment about $P$ caused by the weight of the sign.
(b(ii)(1))[1]
State what is meant by centre of mass.
(b(ii)(2))[2]
Calculate the weight of the concrete block.
(c)[2]
State and explain how the moment about point $P$ due to the weight of the sign changes as it rotates.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Either $W = mg$ or $3.4 \times 10^3 \times 10$” …