moment of inertia

The moment of inertia of a rigid body is a quantity that determines the torque needed for a desired angular acceleration about a given rotational axis, in close analogy to the way mass determines the force needed for a desired acceleration.

Stresses due to vertical shearing forces also depend on moment of inertia and are discussed in Chapter 8.

Some mathematicians and stress analysts use the term second moment of area instead of moment of inertia. That term is, in fact, more descriptive of the definition of this property in the following discussion.