c
$w_{1}=\sqrt{\frac{k}{m_{1}}}=\sqrt{\frac{1200}{3}}=20 \mathrm{rad} / \mathrm{s}$
$\omega_{2}=\sqrt{\frac{1200}{27}}=\frac{20}{3} \operatorname{rad} / s$
$\pi-\theta=\frac{20}{3} t$
$\pi+\theta=20 t$
$2 \pi=\left(20+\frac{20}{3}\right) t$
$t=\frac{6 \pi}{80}=\frac{3 \pi}{40} \mathrm{sec}$
