Question

State the condition under which theorem of parallel axis and theorem of perpendicular axis applicable ?

Answer 1

Dear Student

Perpendicular axis theorem is only valid for planar objects. This does not mean that it only be applied to 2-D objects. This theorem can also be applied to a differential element of a 3-D object also. So, whatever you consider in the question, be it some plane lamina, or a differential element of a 3-D object, perpendicular axis theorem can be used, provided the surface you are using is planar.

Theorem of parallel axes expresses MI about a parallel axis in terms of the MI about a parallel axis passing through COM. Thus, we should ensure that one of the two parallel axes be through the COM of the rigid body.
This is condition of parallel axis theorem.
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