When an object moves, we say the object has kinetic energy by way of its motion. Its kinetic energy is a result of both its velocity and its mass.
If the motion is translational, then how that mass is distributed in the object is inconsequential and we use the object's centre of mass (CoM) as a reference point.
However, if an object is moving ROTATIONALLY then how the mass is distributed around its CoM is an important consideration.
This leads the term, moment of inertia
If the motion is translational, then how that mass is distributed in the object is inconsequential and we use the object's centre of mass (CoM) as a reference point.
However, if an object is moving ROTATIONALLY then how the mass is distributed around its CoM is an important consideration.
This leads the term, moment of inertia
We now can introduce the idea of moment of inertia.
Moment of Inertia is the rotational equivalent to mass, in a rotational situation. This video examines how it works.