a
When similar poles are on same side time period of oscillation \(T _{1}\) is given by \(T _{2}=2 \pi \sqrt{\frac{ I _{1}+ I _{2}}{\left( m _{1}+ m _{2}\right) B _{ H }}}\)

\(m _{1}=2 m , m _{2}= m\)

\(T _{2}=2 \pi \sqrt{\frac{ I _{1}+ I _{2}}{(3 m ) B _{ H }}}\)

When the polarity of magnet is reversed, time period of oscillation \(T _{2}\) is given by

\(T _{2}=2 \pi \sqrt{\frac{ I _{1}+ I _{2}}{\left( m _{1}- m _{2}\right) B _{ H }}}\)

\(T _{2}=2 \pi \sqrt{\frac{ I _{1}+ I _{2}}{ m B _{ H }}}\)

From above Equations

\(T _{1}< T _{2}\)