Reflection & Mirrors question from MHT CET 2025 (25 Apr, Shift 1)

Answer: (d)

1. Convex mirror: $f = +10\text{ m}$. Use $\frac{1}{u} = \frac{1}{f} - \frac{1}{v}$.
2. $v = \frac{25}{3}$: $\frac{1}{u} = \frac{1}{10} - \frac{3}{25} = -\frac{1}{50} \Rightarrow u = -50\text{ m}$
3. $v = \frac{50}{7}$: $\frac{1}{u} = \frac{1}{10} - \frac{7}{50} = -\frac{1}{25} \Rightarrow u = -25\text{ m}$
4. Speed $= \frac{25}{30} = \frac{5}{6}\text{ m/s} = \frac{5}{6} \times \frac{18}{5} = 3\text{ km/hr}$
5. So the answer is (d) 3.