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List of moments of inertia
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List of moments of inertia : ウィキペディア英語版
List of moments of inertia
In physics and applied mathematics, the mass moment of inertia, usually denoted by , measures the extent to which an object resists rotational acceleration about a particular axis, and is the rotational analogue to mass. Mass moments of inertia have units of dimension ML2(() × ()2). It should not be confused with the second moment of area, which is used in bending 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.
x^2 = \mu x^2
|-
| Rod of length ''L'' and mass ''m'', rotating about its center.
This expression assumes that the rod is an infinitely thin (but rigid) wire. This is a special case of the thin rectangular plate with axis of rotation at the center of the plate, with ''w'' = ''L'' and ''h'' = ''0''.
| align="center"|170px
| I_ \,\!  〔
|-
| Rod of length ''L'' and mass ''m'', rotating about one end.
This expression assumes that the rod is an infinitely thin (but rigid) wire. This is also a special case of the thin rectangular plate with axis of rotation at the end of the plate, with ''h'' = ''L'' and ''w'' = ''0''.
| align="center"|170px
| I_ \,\!  〔
|-
| Thin circular hoop of radius ''r'' and mass ''m''.
This is a special case of a torus for ''b'' = 0 (see below), as well as of a thick-walled cylindrical tube with open ends, with ''r''1 = ''r''2 and ''h'' = 0.
| align="center"|170px
| I_z = m r^2\!
I_x = I_y = \frac\,\!
|-
| Thin, solid disk of radius ''r'' and mass ''m''.
This is a special case of the solid cylinder, with ''h'' = 0. That I_x = I_y = \frac\, is a consequence of the Perpendicular axis theorem.
|align="center"| 170px
| I_z = \frac\,\!
I_x = I_y = \frac\,\!
|-
| Thin cylindrical shell with open ends, of radius ''r'' and mass ''m''.
This expression assumes that the shell thickness is negligible. It is a special case of the thick-walled cylindrical tube for ''r''1 = ''r2.
Also, a point mass ''m'' at the end of a rod of length ''r'' has this same moment of inertia and the value ''r'' is called the radius of gyration.


|align="center"| File:moment of inertia thin cylinder.png
| I = m r^2 \,\!  
|-
|Solid cylinder of radius ''r'', height ''h'' and mass ''m''.
This is a special case of the thick-walled cylindrical tube, with ''r''1 = 0. (Note: X-Y axis should be swapped for a standard right handed frame).
|align="center"| 170px
|I_z = \frac\,\!  〔
I_x = I_y = \frac \left(3r^2+h^2\right)
|-
| Thick-walled cylindrical tube with open ends, of inner radius ''r''1, outer radius ''r''2, length ''h'' and mass ''m''.
|align="center" rowspan="2" | File:moment of inertia thick cylinder h.svg
|
I_z = \frac \left(r_1^2 + r_2^2\right) = m r_2^2 \left(1-t+\frac\right)  

〔(Classical Mechanics - Moment of inertia of a uniform hollow cylinder ).
LivePhysics.com. Retrieved on 2008-01-31.〕


where ''t'' = (''r2–r1'')/''r2'' is a normalized thickness ratio;


I_x = I_y = \frac \left(3\left(^2 + ^2\right)+h^2\right)
|-
| With a density of ''ρ'' and the same geometry
| I_z = \frac \left(^4 - ^4\right)

I_x = I_y = \frac \left(3(^4 - ^4)+h^2(^2 - ^2)\right)
|-
| Regular tetrahedron of side ''s'' and mass ''m''
|align="center"| 170px
| I_ = \frac\,\!
I_ = \frac\,\!
|-
| Regular octahedron of side ''s'' and mass ''m''
|align="center"| 170px
| I_=I_=I_ = \frac\,\!
I_=I_=I_ = \frac\,\!
|-
| Regular dodecahedron of side ''s'' and mass ''m''
|align="center"|
| I_=I_=I_ = \frac
I_=I_=I_ = \frac\,\! (where \phi=\frac)
|-
| Regular icosahedron of side ''s'' and mass ''m''
|align="center"|
| I_=I_=I_ = \frac
I_=I_=I_ = \frac\,\!
|-
| Hollow sphere of radius ''r'' and mass ''m''.
A hollow sphere can be taken to be made up of two stacks of infinitesimally thin, circular hoops, where the radius differs from ''0'' to ''r'' (or a single stack, where the radius differs from ''-r'' to ''r'').
|align="center"| 170px
|I = \frac\,\!  〔
|-
| Solid sphere (ball) of radius ''r'' and mass ''m''.
A sphere can be taken to be made up of two stacks of infinitesimally thin, solid discs, where the radius differs from 0 to ''r'' (or a single stack, where the radius differs from ''-r'' to ''r'').
|align="center"| 170px
|I = \frac\,\!  〔
|-
| Sphere (shell) of radius ''r''2, with centered spherical cavity of radius ''r''1 and mass ''m''.
When the cavity radius ''r''1 = 0, the object is a solid ball (above).
When ''r''1 = ''r''2, \left(\frac \left(b^2+c^2\right)\,\!

I_b = \frac \left(a^2+c^2\right)\,\!

I_c = \frac \left(a^2+b^2\right)\,\!
|-
| Thin rectangular plate of height ''h'', width ''w'' and mass ''m''
(Axis of rotation at the end of the plate)
|align="center"| 170px
|I_e = \frac \left(4h^2 + w^2\right)\,\!
|-
| Thin rectangular plate of height ''h'', width ''w'' and mass ''m''
(Axis of rotation at the center)
|align="center"| 170px
|I_c = \frac \left(h^2 + w^2\right)\,\!  〔
|-
| Solid cuboid of height ''h'', width ''w'', and depth ''d'', and mass ''m''.
For a similarly oriented cube with sides of length s, I_ = \frac\,\!
|align="center"| File:moment of inertia solid rectangular prism.png
|I_h = \frac \left(w^2+d^2\right)

I_w = \frac \left(d^2+h^2\right)

I_d = \frac \left(w^2+h^2\right)
|-
| Solid cuboid of height ''D'', width ''W'', and length ''L'', and mass ''m'', rotating about the longest diagonal.
For a cube with sides s, I = \frac\,\!.
|align="center"| 140px
|I = \frac\left(\frac\right)
|-
| Triangle with vertices at the origin and at P and Q, with mass ''m'', rotating about an axis perpendicular to the plane and passing through the origin.
|
|I=\frac(\mathbf\cdot\mathbf+\mathbf\cdot\mathbf+\mathbf\cdot\mathbf)
|-
| Plane polygon with vertices P1, P2, P3, ..., P''N'' and mass ''m'' uniformly distributed on its interior, rotating about an axis perpendicular to the plane and passing through the origin.
|align="center"| 130px
|I=\frac\left(\frac\|\mathbf_\times\mathbf_\|\left(\left(\mathbf_\cdot\mathbf_\right)+\left(\mathbf_\cdot\mathbf_\right)+\left(\mathbf_\cdot\mathbf_\right)\right)}\|\mathbf_\times\mathbf_\|}\right)
|-
| Plane regular polygon with ''n''-vertices and mass ''m'' uniformly distributed on its interior, rotating about an axis perpendicular to the plane and passing through the origin. ''a'' stands for side length.
|align="center"|
|I=\frac\left(1 + 3\cot^2\left(\tfrac\right)\right)  〔}〕
|-
| Infinite disk with mass normally distributed on two axes around the axis of rotation with mass-density as a function of ''x'' and ''y'':
:\rho(x,y) = \tfrac\, e^\,,
|align="center"| 130px
| I = m (a^2+b^2) \,\!
|-
| Uniform disk about an axis perpendicular to its edge.
|align="center"|
| I = \frac 〔http://www.pas.rochester.edu/~ygao/phy141/Lecture15/sld010.htm〕
|}



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