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Torque about a line

  1. Sep 30, 2009 #1
    I know how to find a torque at any one point, and about the x,y, and z axis.

    General equation is t = n dot (r X F)

    where t is the torque, n is unit vector

    I know that to find torque about any axis, suppose the y axis then n=(0,1,0) However, I dont know how to find n of any line.
    I am working on a practice problem for a test where the line is x/2 = y/1 = z/-2

    Any help would be appreciated.
  2. jcsd
  3. Oct 1, 2009 #2
    find 2 points on the line, use the position vector of point2 - point1.

    If this vector has length 1 you're done. If not, multiply the vector by
    some constant to make the length equal to 1.
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