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Distribution of mass about the axis of rotation o The position and orientation of the axis of rotation .
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The radius of gyration of a body about an axis may be defined as the distance from the axis of a mass point whose mass is equal to the mass of the whole body and whose moment of inertia is equal to the moment of inertia of the body about the axis .
o I = M k 2 , where k is radius of gyration . Theorem of perpendicular axis o
Perpendicular Axis Theorem : The moment of inertia of a planar body ( lamina ) about an axis perpendicular to its plane is equal to the sum of its moments of inertia about two perpendicular axes concurrent with perpendicular axis and lying in the plane of the body .
o Applicable only to planar bodies .