\({L_i} = {L_f}\)
\(\left( {\frac{{M{\ell ^2}}}{{12}}} \right){\omega _0} = \left[ {\frac{{M{\ell ^2}}}{{12}} + 2\left( {m{{\left( {\frac{{{\ell ^2}}}{2}} \right)}^2}} \right)} \right]{\omega _f}\)
\( \Rightarrow \,{\omega _f} = \left( {\frac{M}{{M + 6m}}} \right){\omega _0}\)