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Homework Help: Rotational bridge question

  1. Apr 16, 2007 #1
    1. The problem statement, all variables and given/known data
    A uniform bridge 20 m long and weighing 4.00x10^5N is supported by two pillars located 3 m from each end. If a 1.96x10^4 N car is parked 8 m from one end of the brige, how much force does each pillar exert?

    2. Relevant equations
    (Fgb*L/2+Fgp*d)/L(sin theta).

    3. The attempt at a solution
    4x10^5*10+1.96x10^4*8/20(sin 90)=207840
    That's what I got as an answer. I dont know if this is correct though. Any help is appreciated. Thank you.
  2. jcsd
  3. Apr 16, 2007 #2


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    Homework Helper

    No you don't have all of your distances right. The car is 8 m from one end, but how far is it from the pivot point you've chosen (one of the pillars)? Also, the distance of the normal force of the pillar to the pivot point is not 20 m. Draw a diagram and label everything carefully.

    Repeat for the other pillar, the answer will be different.
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