Question 8: Explain the significance of moment of inertia in rotatory motion. ANSWER If ‘m’ is the mass of a particle moving in a circle of radius of ‘r’, then the moment of inertia ‘I’ is given by, We know that, Where α is the angular acceleration and τ is the torque. As angular acceleration α determines the change in the state of rotational motion (whether the rotational motion increases or decreases), and it depends inversely on moment of inertia ‘I’. Therefore, we can define ‘I’ as; Moment of inertia is the property of a rotating body by virtue of which it maintains its state of rest or state of uniform rotational motion. This indicates the significance of moment of inertia in the rotatory motion of a body. Greater the moment of inertia, harder it will be to make change in the state of rest or uniform rotation of the body. We see moment of inertia plays the same role as the mass plays in the linear motion. (Because, heavier the mass difficult it will be to make change in the state of rest or uniform linear motion of a body).