Question

We sometimes use the moment caused by the force so as to determine the moment of inertia of the body. The moment is the cross product of which two vectors?

(a) Force and Radius vectors

(b) Radius and Force vectors

(c) Force and Radius scalars

(d) Radius and Force scalars

I had been asked this question in an interview for job.

My doubt is from Moment of Inertia for Composite Areas topic in portion Moments of Inertia of Engineering Mechanics

Answer 1

Right answer is (b) Radius and Force vectors

The explanation is: The cross product needs to take in the proper sequence. If not taken then the answer is just the opposite of the true answer. That’s why, the answer is not the Force and Radius vectors, but the Radius and Force vectors. Because the moment has its direction, as many of the cross products have, and thus precaution needs to be taken.