Magnetic Properties of Matter: Practice Problem & Solution

Solution Explained:

To solve this problem, we apply the core principles of Magnetic Properties of Matter. Understanding the underlying formula is key to arriving at the correct answer below:

Time period is given by $T = 2\pi \sqrt{\frac{I}{MB}}$. Moment of inertia $I$ is directly proportional to mass $m$. If mass is quadrupled, $I$ becomes $4I$.
New period $T' = 2\pi \sqrt{\frac{4I}{MB}} = 2T$. The restoring torque is still $-MB \sin \theta$, so motion remains S.H.M.