# 9.     A solid sphere of mass M, radius R and having moment of inertia about an axis passing through the centre of mass as I, is recast into a disc of thickness t, whose moment of inertia about an axis passing through its edge and perpendicular to its plane remains I. Then, radius of the disc will be        (A) 2R/√15        (B) R√(2/15)        (C) 4R/√15        (D) R/4

Grade:Upto college level

## 1 Answers

Badiuddin askIITians.ismu Expert
148 Points
14 years ago

Dear Mainak

moment of inertia of solid sphere I =2/5 MR2

mass will remain conserve

let the new radius is R1

so I = MR12/2 + MR12

=3/2 MR12

so 3/2 MR12 =2/5 MR2

R1 =2R/√15

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