A magnet is cut in three equal parts by cutting it perpendicular to its length. The time period of the original magnet is T0 in a uniform magnetic field B. Then, the time period of each part in the same magnetic field is?

Initially the time period of magnet=T0=2π√(I/MB) where I is the moment of inertia of the bar magnet, M is the magnetic moment of the bar magnet.
When the magnet is cut in three equal parts, the magnetic moment of each bar becomes M/3=M'.
Also the new moment of inertia becomes I'=I/9=I/27.
Hence, the new time period becomes T'=2π√(I'/M'B) = T0/3