1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Statics - Coplanar Force Systems

  1. Sep 17, 2009 #1
    The problem statement:
    [​IMG]

    My relevant equation:

    [itex]\phi[/itex] will be the angle between the X axis and [itex]F_{CO}[/itex]

    [tex]\theta = \phi + \arcsin\left(\frac{3}{5}\right)[/tex]

    My attempt at a solution:

    [tex]\Sigma F_{x} = 0:[/tex]

    [tex]F_{CO}\cos\phi - F_{BO}\frac{4}{5} = 0[/tex]

    [tex]F_{CO} = \frac{F_{BO}\frac{4}{5}}{\cos\phi}[/tex]

    [tex]\Sigma F_{y} = 0:[/tex]

    [tex]F_{AO} - F_{BO}\frac{3}{5} - F_{CO}\sin\phi = 0[/tex]

    Combining terms and substituting the equation found for [itex]\Sigma F_{x} = 0[/itex] into [itex]\Sigma F_{x} = 0:[/itex]

    [tex]F_{AO} - \frac{3}{5}F_{BO} - \frac{4}{5}F_{BO}\tan\phi = 0[/tex]

    [tex]9kN - \frac{3}{5}8kN - \frac{4}{5}8kN\tan\phi = 0[/tex]

    [tex]\phi = \arctan\left(\left(9+\frac{24}{5}\right)*\frac{5}{32}\right)[/tex]

    [tex]\phi = 65.12^{\circ}[/tex]

    [tex]\theta = 102^{\circ}[/tex]

    The published value of [itex]\theta[/itex]:

    [tex]\theta = 70.1^{\circ}[/tex]

    I don't know what I did wrong.

    TIA for any response.
     
    Last edited: Sep 17, 2009
  2. jcsd
  3. Sep 17, 2009 #2

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    that plus 24/5 should be a minus 24/5.
    you did well, just missed the sign.
     
  4. Sep 17, 2009 #3
    Jay, thank you sir!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Statics - Coplanar Force Systems
Loading...