A bar magnet has a magnetic moment equal to `65xx10^(-5)` wever `x` metre. 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`seconds. The moment of inertia of the magnet is:

Options

A. `22.5 kg- m^(2)`
B. `11.25 kg- m^(2)`
C. `5.62 kg- m^(2)`
D. `7.16 xx 10^(-7) kg- m^(2)`

Answer

D

Explanation

`T= 2pi sqrt((I)/(MB))`
`rArr I= (T^(2) MB)/(4pi^(2))= ((15)^(2) xx 8pi xx 10^(-4) xx 5 xx 10^(-5))/(4pi^(2))`
`=7.16 xx 10^(-7) kg m^(2)`