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6.System of Particles and Rotational Motion
hard
One end of rod of length $L$ is on horizontal plane. It is inclined at angle $\alpha$ to horizontal plane. When released its angular velocity after coming to horizontal plane is
A
$\sqrt{\frac{3g \sin \alpha}{L}}$
B
$\sqrt{\frac{2L}{3g \sin \alpha}}$
C
$\sqrt{\frac{6g \sin \alpha}{L}}$
D
$\sqrt{\frac{L}{g \sin \alpha}}$
Solution

Energy balance method
$\operatorname{mg} \frac{\mathrm{L}}{2} \sin \alpha=\frac{1}{2} \mathrm{I} \omega^{2}$
$m g \frac{L}{2} \sin \alpha=\frac{1}{2} \frac{m L^{2}}{3} \omega^{2}$
$\omega=\sqrt{\frac{3 g \sin \alpha}{L}}$
Standard 11
Physics