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MHT CET202014 Oct 2020Evening ShiftPhysicsRotational MotionActual

A solid sphere of mass 'M' and radius 'R' has moment of inertia 'l' about its diameter. It 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'. Radius of the disc will be

Options

  1. AR / 19
  2. BR / 15
  3. C2 R / 15
  4. D2 R / 19

Correct answer

C. 2 R / 15

Step-by-step solution

Moment of inertia of solid sphere is I _ s = 2 5 MR ² Moment of inertia of the disc is given by about the given axis is aligned I _ d &= 3 2 Mr ² r ² &= 4 15 R ² 3 2 Mr ²= 2 5 MR ² r &= 2 R 15 aligned

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