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Homework Help: Short Question about Torque on a Ladder Hinge

  1. Nov 16, 2014 #1
    1. The problem statement, all variables and given/known data
    So this is a small part of a much larger problem that I'm working on that I don't want to post here. Basically, I want to find the contribution to the torque about the hinge of a ladder BY the mass of the ladder itself. A ladder is propped open at an angle α. What is the torque about the hinge of the top of the ladder of length L by the ladder itself?

    2. Relevant equations
    τ = r x F

    3. The attempt at a solution
    Will the torque from one side of the ladder I'm ignoring the other side of the ladder for now). be M_ladder / 2 * g * L/2 sinα ? I'm basically wondering what to put for r, the perpindicular distance from the force applied to the point of torque. Should it just be the center of that side of the ladder? In that case, should it be Lsinα /2?
  2. jcsd
  3. Nov 16, 2014 #2


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    Homework Helper

    Are alpha the angle one leg encloses with the vertical, and M the total mass of the ladder? In that case, the expression for the torque due to the weight is correct.
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