May/June 2026 Paper 42

Two particles, $A$ and $B$, of masses $2.5\mathrm{kg}$ and $3.5\mathrm{kg}$ respectively are at rest on a straight smooth horizontal track. Particle $B$ is situated $9\mathrm{m}$ from a vertical wall which is fixed at right angles to the track. Particle $A$ is projected directly towards $B$ with a speed of $3m/s$. In the subsequent motion, $A$ collides and coalesces with $B$ to form particle $C$. Particle $C$ then collides directly with the wall and rebounds. The collision of $C$ with the wall reduces the speed of $C$ by $25\%$.