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Question:

A thin circular disk is in the xy-plane as shown in the figure. The ratio of its moment of inertia about z and z' axes will be?

1:2

1:4

1:3

1:5

Solution:

We know that, the moment of inertia of the circular disk about the center is
MZ = MR²/2
Using parallel axis theorem,
M'Z = MR²/2 + MR² = 3MR²/2
MZ/M'Z = 1/3