Physical significance of moment of inertia:

According to Newton’s 1st law of motion, the stationary object is fixed forever and the moving object continues to move along a straight line with constant speed, unless the object is forced to change its state of rest or of uniform motion by an external force. Greater the mass of the body, greater will be the force required to change its state. So the mass of the body can be taken as the measure of its inertia for translatory motion.
Again in case of rotational motion, due to the rotational inertia, the body will continue in its state of rotational motion. Similarly, greater the moment of inertia of the body, greater will be the amount of torque required to change the state of uniform rotational motion of the body. The moment of inertia of a body about an axis depends on both, the mass of the body and the distribution of mass about the axis of rotation. So the role of moment of inertia in rotational motion is the same as the role of mass in linear motion.