Question

Choose the correct one.

(a) In a coplanar system the moment of the force is chose about a point instead of axis

(b) In a coplanar system the moment of the force is chose about an axis instead of a point

(c) In a 3D system the moment of the force is chose about a point instead of axis

(d) In a 3D system the moment of the force is chose about an axis which is perpendicular to the direction of the force

I had been asked this question in a job interview.

I'd like to ask this question from Moment of a Force in chapter Force System Resultants of Engineering Mechanics

Answer 1

Correct answer is (a) In a coplanar system the moment of the force is chose about a point instead of axis

To explain I would say: The coplanar system means the consideration is with the 2D only. No 3D. Thus if there is any moment needed to be considered we need to take it along the point and not along the axis. But talking about the axis, there might be no axis in the 2D, as it is only in the 3D.