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Homework Help: Torque and Plank

  1. Jun 13, 2008 #1
    A uniform plank of length 5.2 m and weight 213 N rests horizontally on two supports, with 1.1 m of the plank hanging over the right support (see the drawing). To what distance x can a person who weighs 445 N walk on the overhanging part of the plank before it just begins to tip?

    I know you have to set the torque of the plank equal to the torque of the man and solve for his lever length. I just dont know how to get the torque of the plank.
     
  2. jcsd
  3. Jun 13, 2008 #2

    Doc Al

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    Staff: Mentor

    Where does the weight of the plank effectively act?
     
  4. Jun 13, 2008 #3
    the center! so i have to find the difference between the center point and the piece hanging off the side?
     
  5. Jun 13, 2008 #4

    Doc Al

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    Staff: Mentor

    Yes. Hint: Choose the right support as the pivot point for calculating torques. How far from that point is the center of mass of the plank?
     
  6. Jun 13, 2008 #5
    2.6-1.1 = 1.5 m. Thanks!
     
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