RRB Technician Grade 1 Model Paper 1

Concept:When a stone is thrown horizontally, its vertical motion is independent of its horizontal motion.Vertical motion is uniformly accelerated under gravity, while horizontal motion has constant speed.Explanation:First, calculate the time taken to fall using the vertical motion equation:$$s = ut + \frac{1}{2}a t^{2}$$Here, $u = 0$ (since the stone is thrown horizontally), $a = g = 10\ \mathrm{m/s^2}$, and $s = 20\ \mathrm{m}$.Substituting the values:$$20 = 0 \cdot t + \frac{1}{2} \cdot 10 \cdot t^{2}$$This simplifies to $20 = 5t^{2}$, so $t^{2} = 4$, giving $t = 2\ \mathrm{s}$.During this time, the horizontal speed remains constant at $12\ \mathrm{m/s}$.Therefore, the horizontal distance from the building is:$$R = \text{horizontal speed} \times \text{time} = 12 \times 2 = 24\ \mathrm{m}$$Answer:$\mathbf{R = 24\ m}$, which corresponds to Option C.