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Homework Help: Statics machine equilibrium: support reaction- I have too many unknowns

  1. Aug 28, 2011 #1
    Please help Due in 2 hours. Statics machine equilibrium: reactions- too many unknowns

    1. The problem statement, all variables and given/known data
    The woman using the lat pulldown machine is holding the 80-lb weight stationary in the position shown. What are the reactions at the built-in support E and pin support F? (A and C are pinned connections)

    3. The attempt at a solution

    First, I isolated the pulleys and rope to find the components of the tension at D.
    Dx=80cos60=40 lb
    Dy=-40√3 lb

    Then I set up my three equilibrium equations:

    ∑ME=0= -(80 lb)(13/6 ft) - (40√3 lb)(17/3 ft) - (40 lb)(27/4 ft) + ME + Fy(25/6 ft)

    ME= (680√3)/3 +1330/3 + (25/6)Fy

    ∑Fx= 0 = Ex + Fx + (40 lb)

    ∑Fy= 0 = Ey + Fy - (80 lb) - (40√3 lb)

    Right now, I have 3 equations and 5 unknowns, Ex, Ey, ME, Fx, and Fy.

    I'm probably supposed to break it up into two systems, first just the top portion. But I'm not really sure how to proceed from here.

    Thank you!

    Attached Files:

    Last edited: Aug 29, 2011
  2. jcsd
  3. Aug 29, 2011 #2
    Please help. Due in 45 minutes.
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