# moment of inertia

The moment of inertia *I* of a body about any axis is the sum of
the products of the mass *dm* of each
element of the body and the square of *r*, its distance between the
axis. *I* = Σ*r*^{ 2}*dm*. Finding this
distribution of mass is important when determining the force needed to make
the object rotate. See also angular
momentum.