A disc of radius R and thickness R/6 has moment of inertia / about an axis passing through its centre and perpendicular to its plane. Disc is melted a
A disc of radius R and thickness R/6 has moment of inertia / about an axis passing through its centre and perpendicular to its plane. Disc is melted and recast into a solid sphere. The moment of inertia of a sphere about its diameter is
A. `(I)/(5)`
B. `(I)/(6)`
C. `(I)/(32)`
D. `(I)/(64)`
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Correct Answer - A
`(4pi)/(3)R_(1)^(3)=Axxt`
`(4pi)/(3)R_(1)^(3)=piR^(2)(R)/(6)`
`R_(1)^(3)=(1)/(8)R^(3)`
`R_(1)=(1)/(2)R`
`I_(1)=(2)/(5)MR_(1)^(2)=(2)/(5)M((R)/(2))^(2)`
`=(2)/(5)(MR^(2))/(4)`
`=(1)/(5)=(MR^(2))/(2)=(I)/(5)`
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