Question

Define moment of inertia. State its SI unit and dimensions.

Answer 1

We know that all physical quantities are classified as linear and angular ones, for linear motions and angular (or rotational) motions respectively.

Inertia of linear motion is defined as the tendency of an object to remain in a state of rest or of a constant linear velocity. Greater the inertia, more force is required to change this state.

The mass is equal to the linear inertia of an object.

Moment of inertia is the inertia of rotation of an object.

It can be defined by applying the same logic.

Moment of inertia is defined as the tendency of an object to remain in a state of rest or of a constant rotational velocity. Greater the moment of inertia, more torque is required to change this state.

Torque in rotational motion plays the same role as force in linear motion.

Its SI unit is $kg.metr{e}^2$

Its dimension is $L^2{M}^1{T}^0$