Rotational Motion Question 12

Question: The moment of inertia of uniform semi-circular disc of mass M and radius r about a line perpendicular to the plane of the disc through the centre is

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Options:

A) 14Mr2

B) 25Mr2

C) Mr2

D) 12Mr2

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Answer:

Correct Answer: D

Solution:

  • [d] The mass of complete (circular) disc is

The moment of inertia of disc about the given axis is

l=2Mr22=Mr2

The disc may be assumed as combination of two semi-circular parts.

Thus, the moment of inertia of a semi-circular part of disc,

l1ll1

l1=l2=Mr22



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