Who calculated the correct diameter for axial deflection using 6000lb force?

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tsukuba
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Homework Statement


I was able to come up with an answer but I am not sure if its right.
I get the value of 3.668 in for diameter and my friend gets 2.117 in.
I get that value because I subtracted 1500 lb from 6000lb to get my force while he used 6000lb as his Force
Who is right and why?
Thank you

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Homework Equations



S= F L / A E

The Attempt at a Solution


First I calculated the deflection in SAB and I got 0.00189 in.
then I calculate SBS
I rearrange the formula to solve for A
For my Force I take 1500lb and subtract 6000
At the end I get a Diameter of 3.668 in.
 

Discussion

My calculations don't agree with either of you. In order to analyze this problem properly, you should draw free body diagrams of each rod.

According to your calculations, the diameter of rod BC should be greater than the diameter of rod AB, which is certainly not implied by the figure illustrating the problem.
 
this is how I drew my FBD and that's how I got my Forces
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It's also important to know if the axial forces are tensile or compressive.