Conservation of mechanical energy $$ \begin{aligned} & \mathrm{mg} \frac{\mathrm{l}}{2} \sin 30^{\circ}=\frac{1}{2} \frac{\mathrm{ml}^2}{3} \cdot \omega^2 \\ \Rightarrow & \omega^2=\frac{3 \mathrm{~g}}{2 \mathrm{l}}=\frac{30}{1} \\ \Rightarrow & \omega=\sqrt{30} \mathrm{rads} / \mathrm{s} \end{aligned} $$