Question

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 :-

• A. Motion remains simple harmonic with time period $=T/2$
• B. Motion remains simple harmonic with time period $=2T$
• C. Motion remains simple harmonic with time
  period $=4T$
• D. Motion remains simple harmonic with time
  period nearly constant.

Answer 1

Answer: (B)

$T=2\pi \sqrt{\frac{I}{M B_{H}}}\Rightarrow T \propto \sqrt{mass}$
$\therefore T \propto \sqrt{4 m}$
$\boxed{T ' = 2 T}$