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How to determine moment axis and direction on a rod in 3d

  1. May 6, 2013 #1
    if i have rod of a certain length. let point (a) on one end of the rod and point (b) on the other end. along the rod axially is the X axis, vertically Y axis and Z is the lateral direction.let force prependicular on x -axis at point (b) and move this force to point (a) which will create a moment. now the question is at which axis will the moment will be? also is the direction of this moment will be clockwise or counter clockwise.
  2. jcsd
  3. May 6, 2013 #2


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    In 3D, for a rod, it is not enough to specify the x axis along the length of the rod. A third point, which is not located on the rod itself, must be used as a reference point. For example, your rod is determined by the points a and b, and this segment may be assumed to be the x-axis. By specifying a third point c which is not on the rod, you may construct a perpendicular to the rod, and this direction could be assumed to be the y-axis. With two axes specified, the z axis, which is mutually perpendicular to x and y axes, can be constructed.
  4. May 7, 2013 #3
    yes you absolutely right i must put a third point in consideration> your assumptions is what i mean now how to determine moment axis and also its direction if i want to move this force to point (a) which assumed to be parallel to y -axis and perpendicular to x -axis at point (b)
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