Solid Mechanics(Stress Question)

[zack7]

Homework Statement

In the picture below

Homework Equations

Stress=P/A

The Attempt at a Solution

I equated stress AB=-stress BC
p/pi=-(p-60 kips)/2.25pi

P=18.4615kips
This is not the right answer according to the book

 

[zack7]

Does anybody know whether my answer is right or wrong?

Thank you

 

[PhanthomJay]

Well you have the correct equations...so let's check the math;;;
P/pi = (60-P)/2.25(pi)
2.25P = 60 -P
3.25P = 60
P = 18.5 K

Looks Good!

 

[zack7]

But for my homework, I got this question wrong and in the book the answer is 28.2kips

 

[PhanthomJay]

I don't know where that answer comes from...If P =28.2 K, then the force in the fat shaft would be woul be 31.8 K compression; and the tensile stress in the thin shaft would be 9 ksi, while the compressive stress in the fat one would be 4.5 ksi...far from equal in magnitude... off by a factor of 2..

 

[nvn]

zack7: Nice work. I currently agree with your answer in post 1, and with the answer by PhanthomJay[/color]. The answer in the book currently appears wrong.