Inertia of a Body Depends upon
Mass of the body
Inertia is the resistance of any physical object to any change in its state of motion, including changes to its speed and direction. It is the tendency of objects to keep moving in a straight line at constant velocity. The principle of inertia is one of the fundamental principles of classical physics that are used to describe the motion of objects and how they are affected by applied forces. Inertia comes from the Latin word, iners, meaning idle, sluggish. Inertia is one of the primary manifestations of mass, which is a quantitative property of physical systems.
Factors which determine the Moment of Inertia of a body-
The mass of the body. Experiments show that I is directly proportional to the mass
The distribution of mass in the body.
The moment of inertia of a body is directly proportional to its mass and increases as the mass is moved further from the axis of rotation.The fact that I depends on mass distribution means that the same body can have different moments of inertia depending on which axis of rotation we consider.