| Name | Picture | Dimensions | Defining Equation | Principal Moments about O | ||
|---|---|---|---|---|---|---|
| Ix | Iy | Iz | ||||
| Uniform Rod |
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length, 2a | x = y = 0
-a < z < a |
1/3Ma2 | 0 | |
| Circular Rim |
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radius, a | x2 + y2 = a2
z = 0 |
1/2Ma2 | Ma2 | |
| Circular Disk |
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radius, a | x2 + y2 < a2
z = 0 |
1/4Ma2 | 1/2Ma2 | |
| Rectangular Lamina |
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width, 2a
length, 2b |
-a < x < a
-b < y < b z = 0 |
1/3Mb2 | 1/3Ma2 | 1/3M(a2+b2) |
| Elliptical Disk |
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principal semi-axes, a and b |
(x/a)2 + (y/b)2 < 1
z = 0 |
1/4Mb2 | 1/4Ma2 | 1/4M(a2+b2) |
| Annulus | ![]() |
radii, b < a | b2 < x2 + y2 < a2
z = 0 |
1/4M(a2+b2) | 1/2M(a2+b2) | |