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Holding up a sign

  1. Mar 24, 2015 #1
    1. The problem statement, all variables and given/known data
    You are holding a sign as shown below. The sign (including the horizontal bar it hangs from) has a mass of 1.80 kg and is 36.5 cm wide. The sign is hanging from a 1.30 m tall, 4.16 kg vertical post. The sign is symmetric with a uniform mass distribution as implied by the drawing.
    Q0vSIDa.png
    What external force (+ if up, - if down) and torque (+ for CCW, - for CW) do you have to apply with your hand to keep the sign in static equilibrium? [Use g = 9.80 m/s2 and ignore the width of the vertical post.]

    2. Relevant equations
    Torque = Fd = 0

    3. The attempt at a solution
    I'm not quite sure how to deal with the vertical stick.
    Torque = F1d1 - F2d2 - Fd3 = 0
    As far as the set up goes, this is all I've got and I don't think it is correct. I may not be visualizing this problem correctly.
     
  2. jcsd
  3. Mar 24, 2015 #2

    PhanthomJay

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    There is an external unknown vertical reaction force and an unknown torque at your hand. You should identify these as V and T, respectively. Now apply your equilibrium equations to solve for them. Although explain what F1 ,d1 ,etc. are.
     
  4. Mar 25, 2015 #3

    CWatters

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    How about starting with a free body diagram?
     
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