Moment of Inertia

The moment of inertia is also called angular mass, mass inertia, rotational inertia etc. The SI unit of moment of inertia is kg·m². It can be defined as the resistance that any object offers for its rotation and changes. In other words, it can also be defined as the inertia of an object, which is in rotational motion, to its rotations. The moment of inertia has a very major role to play in the field of rotational dynamics. In fact, it is actually used to bring up the relationship between the angular acceleration, torque, angular velocity and angular momentum etc. It is referred with I in most of the cases. In some cases, the symbol of moment of inertia can also be J.

Leonhard Euler is the man who introduced this concept in one of his well known books titled as ‘Theoria motus corporum solidrum seurigidorum’, in the year 1765. There were many other concepts including the inertia’s principal axis being discussed in this book along with the moment of inertia.

The difficulty that an object finds in changing for the angular motion is described in this concept. Hence, it gives a clear picture of the mass of an object in relation to axis. The moment of inertia will increase with the increase in the mass of an object. For instance, imagine that there are two hoops L and S, which are composed using the same material, and the mass of these two hoops are equal. The only difference is that the hoop L has a larger diameter and a thinner body compared to the hoop S. If this is the case, then the effort required to change the angular motion of hoop L will be more when compared to the effort required to change the hoop S. The reason is that the mass distribution in the hoop L will be done quite far from its axis.

Questions:

• What are the two symbols used to refer Moment of Inertia?
• Who introduced the concept Moment of Inertia?