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Homework Help: Ladder Equilibrium Problem

  1. Mar 28, 2010 #1
    1. The problem statement, all variables and given/known data
    see the attachment below...


    2. Relevant equations
    net force = 0, net torque = 0
    normal force(ground) = ?

    3. The attempt at a solution
    well, so far,,

    net force(y) = normal force(floor) - weight(man) - weight(ladder) + ??(force exerted by hinge?)
    net force(x) = 0 ( ?? )

    Choosing the bottom of ladder as pivot point,
    net torque = weight(ladder) x 2a + weight(man) x a - ??(force by hinge?)




    First of all, sorry for not using latex..

    The hinge is my problem, since I'm not familiar in solving with it.
    What are the forces (and their directions) exerted on the ladder at the hinged point?
    I really don't know..

    And are my assignment of forces correct?

    Thanks in advance..

    I NEED THIS AFTER 10 HOURS...
    So i have no time to reply, so please, I'm begging, please be direct to the point. And i hope each reply will help me..

    Thank you guys..
     

    Attached Files:

  2. jcsd
  3. Mar 28, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: Choose a pivot point that eliminates having to know anything about the forces at the hinge.
     
  4. Mar 28, 2010 #3
    thanks... i overlooked it since i always choose the point of contact with the ground as the pivot..

    normal force = 150N ??

    :)
     
  5. Mar 28, 2010 #4

    Doc Al

    User Avatar

    Staff: Mentor

    You got it. :approve:
     
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