The moment of inertia (symbol I, SI unit kg·m2) of a rotating object is a measure of what angular acceleration will be produced by a given torque, and can therefore be thought of as the rotational equivalent of mass. It is defined as

$ \iiint \rho (r) r^2 dV $

For a point mass, it is equal to the distance from the centre of rotation squared times the mass of the object, or

$ I = mr^2 $

The moment of inertia is also equal to angular momentum divided by angular velocity, or

$ I = \frac{L}{\omega} $