Determining the forces in three cables.

[cavalieregi]

Homework Statement

Homework Equations

The Attempt at a Solution

1. I first found the angles each cable made with the pillar.
2. With these angles I found the components of the forces in the x and y direction.
3. So ∑Fx and ∑Fy were found.
4. Then using these values I equated that
$F = \sqrt(F_x ^2 + F_y ^2)$
5. The from here I subbed Fb and Fc = Fa and that F = 200kN Then rearranging to get Fa I got Fa = 112.36N however it should be 68.4kN.

I am unsure where I have gone wrong. Note vectors are not to be used to solve problem i.e using i, j and k components.

 

[TSny]

Your approach looks good. You must be making an error somewhere in the calculation. I get 68.2 kN for the answer.

 

[cavalieregi]

So could you give me a rough outline of your method.

 

[cavalieregi]

Don't worry I worked it out.