One of the use of the centre of mass or centroid is as in the radius of gyration is that the net force acts at the ___________ of the loading body.

Centroid

In the moment of inertia calculations we see that the net force acts at the centroid of the loading body. That is if the loading system is in the form of the triangle then the at the distance 2 by 3 of the base the net force of the loading will act. And the load will be half the area of the loading.