The moment of inertia of a rigid body is a quantity that determines the torque needed for a given angular acceleration about a given rotational axis, analogous to how mass determines the force needed for a given acceleration.

The moments of inertia of a heterogeneous body whose boundary is a surface of uniform density may sometimes be found by the method of differentiation.

Consequently, the moment of inertia of a body relative to any axis can be found when that for the parallel axis through its centre of gravity is known.

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.

Moment of inertia

Meaning

Noun

Synonyms