Mathematics 9709 · AS & A Level · Forces and equilibrium
Forces and equilibrium — practice question
Block $B$, with mass $7\text{ kg}$, is initially at rest on rough horizontal ground. A force of size $X\text{ N}$ acts on $B$ at an angle of $15^\circ$ to the upward vertical (see diagram).
(i)[2]
Since $B$ is in equilibrium, find, in terms of $X$, the normal component of the force exerted on $B$ by the ground.
(ii)[3]
The coefficient of friction between $B$ and the ground is $0.4$. Find the value of $X$ that makes $B$ in limiting equilibrium.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Vertical force balance on the block gives: $N + X\cos15^\circ = \text{weight of }B$” …