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Homework Help: Torque and Equilibrium.

  1. Oct 14, 2009 #1
    1. The problem statement, all variables and given/known data
    A 70.7 kg woman stands on a very light, rigid board that rests on a bathroom scale at each end. The total length of the board is L=2.1 m, and the woman's distance from the left of the board is 1.3 m.
    What is the reading on the left scale? The right scale?

    2. Relevant equations


    3. The attempt at a solution
    I converted the woman's weight to 693.3 N. For d1 I used half the length of the board, 1.05 m, and for d2, I found the distance the woman was away from the right side of the board relevant to the center of gravity on the board, which was 0.25 m. To find n2, I did
    (693.3N)(1.05m)/1.3m and got 559.97 N.
    I subtracted that amount from the woman's weight and got 133.33 N, which made sense since she was closer to the right side of the board, but the computer says no. Can anyone see what I'm doing wrong? I was following an example in the book.

    Thank you!
  2. jcsd
  3. Oct 14, 2009 #2


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    Homework Helper

    She is standing on a very light board. No neglect its mass.
    Let R1 and R2 are the reactions on the scales. Find the moments due to woman and R2 about R1. Hence find the distance of the woman from R1.
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