Very basic statics question/moment of inertia

  1. Statics: If computing the moment of inertia about the y-axis of a triangular shape in the 2nd quadrant(not touching the x-axis); would i still use hb^3 /12
     
  2. jcsd
  3. SteamKing

    SteamKing 8,789
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    Yes, you would, but be careful which sides you use for 'b' and 'h'. You haven't specified which is measured along the x-axis and which is measured along the y-axis. This formula only works for right triangles, incidentally.

    http://en.wikipedia.org/wiki/List_of_area_moments_of_inertia
     
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  4. nvn

    nvn 2,124
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    encorelui2: So far, your formula looks correct. And, it is not limited to right triangles.

    It does not matter whether it touches the x axis or not. And it does not matter what quadrant it is in. It only needs to have one side coincident (collinear) with the y axis, assuming b is the horizontal width of your triangle.
     
  5. SteamKing

    SteamKing 8,789
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    I apologize for not posting more complete information, but the OP's formula for the moment of inertia of a triangle is indeed only applicable to right triangles. The following link gives formulas for the area properties for more general triangular shapes:

    http://www.efunda.com/math/areas/triangle.cfm
     
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