moment of inertia

Noun

moment of inertia (plural moments of inertia)

1. (classical mechanics) A measure of a rigid body's resistance to change in its angular velocity around a given axis.
   • 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.1882, Edward John Routh, The Elementary Part of a Treatise on the Dynamics of a System of Rigid Bodies, 4th edition, MacMillan & Co., page 10

   Synonyms:

   mass moment of inertia, angular mass, rotational inertia

2. (structural engineering) Second moment of area; a measure of a rigid body's resistance to bending.
   • 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.2007, Robert L. Mott, Applied Strength of Materials, 5th edition, Taylor & Francis (CRC Press), page 323

   Synonyms:

   area moment of inertia, second area moment, second moment of area, second moment of inertia