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A disc of radius R and thickness 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 isA. `l/5`B. `l/6`C. `l/32`D. `l/64` |
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Answer» Correct Answer - A According to question, Moment of inertia of disc is given by `l=(MR^2)/2` [Symbals have their usual meanings.] When the disc is remoulded into solid sphere, then volume remains same. i.e,Volume of disc =Valume of solid sphere i.e `piR^2xxR/6=4/3pir^3` `Rightarrow r^3=R^3/8 Rightarrow r=R/2` Now, moment of inertia of solid sphere is given by `2/5mr^2` `=2/5xxmxxR^2/4=(mR^2)/10` `l/5` [l = moment of inertia of disc] |
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