Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Equilibrium and tension problem

  1. Nov 4, 2004 #1
    The problem as stated in the book
    "Calculate the tension [tex]F_{t}[/tex] in the wire that supports the 30-kg beam shown in fig. 9-57 (attached), and the force [tex]F_{w}[/tex] exerted by the wall on the beam (give magnitude and direction)."

    Getting the Tension in the string was easy.
    [tex]\sum\tau = F_{ty} \cdot x_{1} - mg(\frac{x_{1}}{2}) = 0[/tex]
    [tex]F_{ty} = 147N[/tex]
    [tex]F_{t} = \frac{F_{ty}}{sin 50} = 1.9 \times 10^2N [/tex]

    To get the [tex]F_{w}[/tex], I used the sum of forces.
    [tex]\sum{F_{x}} = F_{tx} - F_{wx} = 0 \Rightarrow F_{tx} = F_{wx} = F_{t} \cdot cos 50 = 123.35 N[/tex]
    [tex]\sum{F_{y}} = F_{ty} + F_{wy} - mg \Rightarrow F_{wy} = mg - F_{ty} = 102.11 N[/tex]

    So now I have the two components for [tex]F_{w}[/tex] , I use pythagorous and solve for the resultant vector to get 160.13 N. The book, however, says the answer is [tex]1.9 \times 10^2 N[/tex]. Can anyone tell me what I'm doing wrong?
     

    Attached Files:

  2. jcsd
  3. Nov 4, 2004 #2
    nevermind, the problem was when I confused [tex]F_{wy}[/tex] for [tex]F_{w}[/tex]
     
    Last edited: Nov 4, 2004
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook