5.5. Newton's second law for rotational motion and its analysis

Taking into account (5.2) and (5.3) the torque of the body

(5.8)

or

This expression is an analogue of Newton's second law for rotational motion, from which it follows that angular acceleration a solid body when rotating around a fixed axis is directly proportional to the torque and inversely proportional to the moment of inertia relative to this axis. From this expression it follows that the moment of inertia U is a measure of its inertia in the rotational motion around a fixed axis. In the case of translational motion, a measure of inertia, as is known, is body mass.