A) 2s
B) \[2/3s\]
C) \[2\sqrt{3\,}s\]
D) \[2/\sqrt{3\,}s\]
Correct Answer: B
Solution :
[b] The moment of inertia of original magnet \[I=\frac{m{{\ell }^{2}}}{12}\] After dividing into three equal parts, \[I'=3(m/3).\frac{{{(\ell /3)}^{2}}}{12}=\frac{I}{9}.\] Also magnetic moment, M' = M Now, \[\frac{T'}{T}=\sqrt{\frac{I'}{I}\times \frac{M}{M'}}\] \[\therefore \,\,\,\,\,\,T'=T\times \sqrt{\frac{I'}{I}}=2\times \sqrt{\frac{I}{9}}=\frac{2}{3}s.\]You need to login to perform this action.
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