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Inertia in 3d

  1. Sep 17, 2015 #1
  2. jcsd
  3. Sep 17, 2015 #2

    SteamKing

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    The formula you attached appears to calculate the second moment of area of a general polygon, using the (x,y) coordinates of the vertices.

    You'll have to be more specific about what you mean by "calculat(ing) inertia in 3d".
     
  4. Sep 17, 2015 #3
    the moment of inertia in 3d is it the same for 2d?
     
  5. Sep 17, 2015 #4

    SteamKing

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    It depends.

    The second moment of area is sometimes referred to as the moment of inertia. This is a property of plane figures.

    The mass moment of inertia for 3-D bodies determines how easy or how difficult it is to accelerate a body in rotation.

    As I asked before, which of these two properties do you wish to calculate in 3-D?
     
  6. Sep 18, 2015 #5
    so there is second moment of inertia and moment of inertia I didn't knew that :/
    of course I'm talking about second moment of inertia in 3d, for different shapes...
     
    Last edited: Sep 18, 2015
  7. Sep 18, 2015 #6

    SteamKing

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    No, you have confused things.

    1. There is a second moment of area for plane shapes, which is also referred to as a moment of inertia. The second moment of area has units of L4.

    https://en.wikipedia.org/wiki/List_of_area_moments_of_inertia

    2. There is a mass moment of inertia for 3-D bodies, which has units of ML2:

    https://en.wikipedia.org/wiki/List_of_moments_of_inertia
     
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