List_of_moments_of_inertia

List of moments of inertia

List of moments of inertia

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Moment of inertia, denoted by I, measures the extent to which an object resists rotational acceleration about a particular axis, it is the rotational analogue to mass (which determines an object's resistance to linear acceleration). The moments of inertia of a mass have units of dimension ML2 ([mass] × [length]2). It should not be confused with the second moment of area, which has units of dimension L4 ([length]4) and is used in beam calculations. The mass moment of inertia is often also known as the rotational inertia, and sometimes as the angular mass.

For simple objects with geometric symmetry, one can often determine the moment of inertia in an exact closed-form expression. Typically this occurs when the mass density is constant, but in some cases the density can vary throughout the object as well. In general, it may not be straightforward to symbolically express the moment of inertia of shapes with more complicated mass distributions and lacking symmetry. When calculating moments of inertia, it is useful to remember that it is an additive function and exploit the parallel axis and perpendicular axis theorems.

This article mainly considers symmetric mass distributions, with constant density throughout the object, and the axis of rotation is taken to be through the center of mass unless otherwise specified.

Moments of inertia

Following are scalar moments of inertia. In general, the moment of inertia is a tensor, see below.

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List of 3D inertia tensors

This list of moment of inertia tensors is given for principal axes of each object.

To obtain the scalar moments of inertia I above, the tensor moment of inertia I is projected along some axis defined by a unit vector n according to the formula:

where the dots indicate tensor contraction and the Einstein summation convention is used. In the above table, n would be the unit Cartesian basis ex, ey, ez to obtain Ix, Iy, Iz respectively.

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See also

Notes

  1. Width perpendicular to the axis of rotation (side of plate); height (parallel to axis) is irrelevant.

References

  1. Raymond A. Serway (1986). Physics for Scientists and Engineers (2nd ed.). Saunders College Publishing. p. 202. ISBN 0-03-004534-7.
  2. Classical Mechanics - Moment of inertia of a uniform hollow cylinder Archived 2008-02-07 at the Wayback Machine. LivePhysics.com. Retrieved on 2008-01-31.
  3. Satterly, John (1958). "The Moments of Inertia of Some Polyhedra". The Mathematical Gazette. 42 (339). Mathematical Association: 11–13. doi:10.2307/3608345. JSTOR 3608345. S2CID 125538455.
  4. Ferdinand P. Beer and E. Russell Johnston, Jr (1984). Vector Mechanics for Engineers, fourth ed. McGraw-Hill. p. 911. ISBN 0-07-004389-2.
  5. Jeremy Tatum. "2.20: Ellipses and Ellipsoids". phys.libretexts.org. Retrieved 1 May 2023.
  6. see e.g. "Moment of Inertia J Calculation Formula". www.mikipulley.co.jp. Retrieved 30 April 2023.
  7. A. Panagopoulos and G. Chalkiadakis. Moment of inertia of potentially tilted cuboids. Technical report, University of Southampton, 2015.

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