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Equilibrium problem help

  1. Aug 18, 2012 #1
    1. The problem statement, all variables and given/known data
    Arlene is to walk across a "high wire" strung horizontally between two buildings 14.0m apart. The sag in the rope when she is at the midpoint is 10.0 degrees. If her mass is 52.0kg , what is the tension in the rope at this point?


    2. Relevant equations
    Fnet=ma
    a=0 so fnet=0

    3. The attempt at a solution
    So I know that Fg=9.8*52=509.6 N, and I broke down Ft into Ftx and Fty. sin10=Fty/Ft but I have no idea how to use Fg in that formula to find Ft.
    In my notes I have "Ft=(m*g)/(2sinθ) which gives the correct answer, but I don't understand how I got that formula. Can someone explain where it came from/give me some guidance. Why 2sin?
     
  2. jcsd
  3. Aug 18, 2012 #2

    Doc Al

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    Staff: Mentor

    Since she is in equilibrium, ƩF = 0. In particular, the y-component of the net force must equal zero.

    What forces act on her? What are their y-components?
     
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