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Laws Of Motion

Question
CBSEENPH11020797

The moment of inertia of a uniform circular disc of radius R and mass M about an axis touching the disc at its diameter and normal to the disc is

  • MR squared
  • 2 over 5 MR squared
  • 3 over 2 MR squared
  • 1 half MR squared

Solution

C.

3 over 2 MR squared

The moment of inertia about an axis passing through centre of mass of disc and perpendicular to its plane is
                     straight I subscript CM space equals space 1 half MR squared
where M is the mass of disc and R its radius. According to theorem of parallel axis, MI of circular disc about an axis touching the disc at it diameter and normal to the disc is
                   straight I equals space straight I subscript CM space plus space MR squared
                     equals 1 half MR squared plus space MR squared
equals 3 over 2 MR squared