• # question_answer A bar magnet is oscillating in the Earth?s magnetic field with a period T. What happens to its period and motion if its mass is quadrupled                                                [CBSE PMT 2003] A)            Motion remains S.H.M. with time period = 2T B)            Motion remains S.H.M. with time period = 4T C)            Motion remains S.H.M. and period remains nearly constant D)            Motion remains S.H.M. with time period $=\frac{T}{2}$

As $T\propto \sqrt{I}$; where I = moment of inertia $=\frac{\text{w}{{L}^{2}}}{12}\Rightarrow T\propto \sqrt{\text{w}}$ (w = Mass of magnet. If $\text{w}\to$quadrupled, then $T\to$doubled i.e. ${{T}^{'}}=2T$