Question

What is parallel axis theorem and to whom it is applied so that it can give the product of inertia of an area?

(a) Theorem used to add the two mutually perpendicular moment of inertias for areas

(b) Theorem used to add the two mutually perpendicular moment of inertias for volumes

(c) Theorem used to add the two mutually perpendicular moment of inertias for linear distances

(d) Theorem used to add the two mutually perpendicular moment of inertias for vectors

I had been asked this question in semester exam.

My enquiry is from Product of Inertia for an Area in chapter Moments of Inertia of Engineering Mechanics

Answer 1

Right option is (a) Theorem used to add the two mutually perpendicular moment of inertias for areas

To explain: Parallel axis for any area is used to add the two mutually perpendicular moment of inertias for areas. It gives a moment of inertia perpendicular to the surface of the body. That is the moment of inertia perpendicular to the surface in considerance.