moment of inertia

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English Wikipedia has an article on:


moment of inertia (plural moments of inertia)

  1. (physics, 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 desired angular acceleration about a given rotational axis, in close analogy to the way mass determines the force needed for a desired acceleration.
    • 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,
      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.
    • 1884, Benjamin Williamson, An Elementary Treatise on the Integral Calculus, 4th Edition, Appleton and Company, page 292,
      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.
  2. (engineering, structural engineering) Second moment of area; a measure of a rigid body's resistance to bending.
    • 2007, Robert L. Mott, Applied Strength of Materials, 5th Edition, Taylor & Francis (CRC Press), page 323,
      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.


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