A bar has a magnetic moment equal to `5xx10^(-5) weberxxm`. It is suspended in a magnetic field which has a magnetic induction (B) equal to `8pixx10^(-4)` tesla. The magnet vibrates with a period of vibration equal to 15 sec. The moment of intertia of the magnet is

Options

A. `22.5 kgxxm^(2)`
B. `11.25xxkgxxm^(2)`
C. `5.62xxkgxxm^(2)`
D. `7.16xx10^(-7)kgm^(2)`

Answer

D

Explanation

Time period of a magnet `T=2pisqrt(I/(MB))`
or `I=(T^(2)MB)/(4pi^(2))=(225x5xx10^(-5)xx8pixx10^(-4))/(4pi^(2))`
`:. I=7.16xx10^(-7) kg m^(2)`