Mathematics 9709 · AS & A Level · Forces and equilibrium
Forces and equilibrium — practice question
Four coplanar forces with magnitudes 20 N, 30 N, 15 N and 25 N act at point P in the directions indicated in Fig. 7.1. They lie in a vertical plane. The combined effect of these forces is a resultant of magnitude $S\text{ N}$, which acts at an angle of $\alpha^\circ$ below the horizontal, as illustrated in Fig. 7.2.
(a)[6]
Find the values of $S$ and $\alpha$.
(b)[5]
A small ring of mass $0.6\text{ kg}$ is threaded on a rough straight horizontal wire. The four forces shown in Fig. 7.1 act on the ring and lie in the same vertical plane as the wire. The ring starts from rest and takes $3\text{ s}$ to cover a distance of $2\text{ m}$ along the wire. Find the coefficient of friction between the ring and the wire.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Try resolving in both directions” …