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A solid sphere of radius R has moment of inertia J about its qeometrical axis. If it is melted into a disc of radius r and thickness t . If its moment of inertia about the tangential axis (which is perpendicular to plane of the disc), is also equal to I , then the value of r is equal to

Options

  1. A2 15 R
  2. B2 5 R
  3. C3 15 R
  4. D3 15 R

Correct answer

A. 2 15 R

Step-by-step solution

2 3 M R^2= 1 2 M r^2+M r^2 or 2 3 M R^2= 3 2 M r^2 r= 2 15 R

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