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Mass moment of solids

  1. Mar 23, 2013 #1

    "The static moments of the solid about the coordinate planes Oxy, Oyz, Oxz are given by the formulas"

    What exactly does that mean? I understand what a moment about an axis is, but about a plane? what? Do they mean moment about two axis at the same time, or something?

    And how did they arrive at the following formulas? http://www.math24.net/images/7tri2.gif [Broken]
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Mar 23, 2013 #2
  4. Mar 23, 2013 #3


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    The integrals give you the average mass density weighted value of each coordinate.

    One shows that these weighted coordinates determine the center of mass. For a rigid body, its kinematics can be reduced to the motion of its center of mass - I think.
  5. Mar 24, 2013 #4
    If a solid has a moment about a plane, what does this mean? I know that you can find the centre of mass in a solid, and then use this point to balance the solid, but how does this relate to "moment about plane"?

    Does the "moment about the xy-plane" simply mean the solid's moment about the x and y axis?
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