Question

If any external force also is applied on the structure and we are determining radius of gyration then what should we consider?

(a) The net force will act at the centroid of the structure only

(b) The net load will not be formed as all the forces will be cancelled

(c) The net force will act on the base of the loading horizontally

(d) The net force will not to be considered, there would be a net force of the distribution, rest will be the external forces

The question was asked in a job interview.

My enquiry is from Radius of Gyration of an Area in portion Moments of Inertia of Engineering Mechanics

Answer 1

The correct option is (d) The net force will not to be considered, there would be a net force of the distribution, rest will be the external forces

To explain: The external forces are treated differently. They are not added by the force of the distributed loading. That is the force not only acts at the centroid always. It can be shifted also. Depending on the external forces. Thus the use of centroid or centre of mass.