Centre Of Mass

The motion of the centre of mass is the result of external forces.

The angular momentum of a particle moving along a circle of radius is
where is the linear momentum of the particle
By the definition of vector product, is perpendicular to .
So the angle between them is .

Step 1: Define the centroid of mass.
The centroid of mass (or center of mass) is the point where the mass of the body can be considered to be concentrated for analysis of motion.

Step 2: Centroid of mass vs centroid of volume.
The centroid of mass depends on the distribution of mass, whereas the centroid of volume is the geometric center.
In this case, the centroid of mass is the correct answer.