A bar magnet is oscillating in the earth's magnetic field with a period T. What happens to its period of motion, if its mass is quadrupled 

 

The time period of a bar magnet in a magnetic Solution: The time period of a bar magnet in a magnetic field is given by. 

$\mathrm{T}=2\pi \sqrt{\frac{I}{\mathrm{MB}}}$;

Here, I = moment of inertia $\alpha$ m , M = moment of magnet, B = magnetic field. 

$\mathrm{T}\propto \sqrt{I}\propto \sqrt{\mathrm{m}}$; so, T becomes twice as mass becomes four times.