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Homework Help: Moment about a point

  1. Sep 19, 2015 #1
    1. The problem statement, all variables and given/known data
    A 100 lb vertical force is applied to the end of a lever, which is attached to a shaft at O. Determine (a) the moment of the 100 lb force about O (b) the horizontal force applied at a that creates the same moment about O.

    2. Relevant equations

    3. The attempt at a solution
    I know the solution but I'm still a bit confused as to what I'm doing for part (a) I have Mo = Fd = 24in*cos(60) * 100 lb
    But I don't understand why I'm using
    24in*cos(60) and not 24in*sin(60)....

  2. jcsd
  3. Sep 19, 2015 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You need the perpendicular distance between O and the line of action of the force.
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