A particle is released from height $S$ above the surface of the earth. At certain height its kinetic energy…
- $\frac{\mathrm{S}}{2}, \sqrt{\frac{3 \mathrm{gS}}{2}}$
- $\frac{\mathrm{S}}{2}, \frac{3 \mathrm{gS}}{2}$
- $\frac{\mathrm{S}}{4}, \frac{3 \mathrm{gS}}{2}$
- $\frac{\mathrm{S}}{4}, \sqrt{\frac{3 \mathrm{gS}}{2}}$
Solution
& \mathrm{V}^2=0+2 \mathrm{~g}(\mathrm{~S}-\mathrm{x}) \\ & \mathrm{V}^2=2 \mathrm{~g}(\mathrm{~S}-\mathrm{x})
\end{aligned}$
At B, Potential energy $=m g x$
$\begin{aligned}
& \mathrm{mgx}=3 \times \frac{1}{2} \mathrm{mv}^2 \\ & \mathrm{gx}=\frac{3}{2} \times 2 \mathrm{~g}(\mathrm{~S}-\mathrm{x}) \\ & 4 \mathrm{x}=\mathrm{S} \\ & \mathrm{x}=\frac{\mathrm{S}}{4}
\end{aligned}$
$\Rightarrow \mathrm{V}=\sqrt{2 \mathrm{~g} \times \frac{3 \mathrm{~S}}{4}}=\sqrt{\frac{3 \mathrm{gS}}{2}}$
Asked in: JEE Main 2025 (03 Apr Shift 1)