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Language:enStatus: Standard
Term: moment of inertia
Synonym1: mass moment of inertia
Symbol: J
Definition: for a body and a specified axis, scalar quantity equal to the integral J = ∫D R2 dm = ∫D R2 ρ dV, where ρ is mass density in a domain D with quasi-infinitesimal mass dm and volume dV, and R is the distance between the domain and the axis

NOTE 1 For a material point, the moment of inertia is equal to the product of its mass m and the square of its distance R to the axis, thus J = mR2. For a system of particles, it is equal to the sum of their moments of inertia.

NOTE 2 In non-relativistic physics, moment of inertia is an additive quantity.

NOTE 3 More generally, moment of inertia can be defined for a rigid body as a tensor quantity J MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqk0di9Wr=fpeei0di9v8qiW7rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiqadQeagaWcgaWcaa aa@39BF@ , where Jxx = −∫(y2 + z2) dm, cycl., cycl., and Jyz = −∫ yz dm, cycl. cycl.

NOTE 4 The moment of inertia is not to be confused with the second axial moment of area and the second polar moment of area.

NOTE 5 The coherent SI unit of moment of inertia is kilogram metre squared, kg·m2.

Publication date:2011-04
Internal notes:2014-07-11: Corrected <i>J</i>, <i>I</i> to <i>J</i><br><i>I</i>. JGO

2017-06-02: Cleanup - Remove Attached Image 113-03-21en.gif
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