May/June 2026 Paper 42

Two particles, $A$ and $B$, of masses $0.5\mathrm{kg}$ and $0.8\mathrm{kg}$ respectively are attached to the ends of a light inextensible string. The string passes over a small smooth pulley fixed at the end of a rough horizontal plane and to the top of a smooth inclined plane. Particle $A$ is held on the horizontal plane, while $B$ lies on the inclined plane, which makes an angle of $55^{\circ }$ with the horizontal. The string is in the same vertical plane as a line of greatest slope of the inclined plane (see diagram). Particle $A$ is released from rest with the string taut. Particle $B$ moves $0.3\mathrm{m}$ down the inclined plane in $0.4\mathrm{s}$.