Physics || JEE Main previous year questions with Solutions

(C) Velocity just before collision = $\sqrt{2 g h}$

Velocity just after collision = $\sqrt{2 g (\frac{h}{2})}$

$∴$ $∆ K E = \frac{1}{2} m (2 g h) - \frac{1}{2} m g h = \frac{1}{2} m g h$

$∴$ % loss in energy $\frac{∆ K E}{K E_{i}} \times 100$

$\Rightarrow \frac{∆ K E}{K E_{i}} \times 100 = \frac{\frac{1}{2} m g h}{\frac{1}{2} m g 2 h} \times 100 = 50 %$

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