Need Help with Mechanical Principles: Calculating Stress, Strain, and Extension

[Curly91]

Hey guys. Just signed up hear after finding the website. I really need some help on Mechanical Principles as i have just been handed work to do once i came back from my car crash. I don't have a clue what any of it means so i could really do with your help.

One of the questions is: A steel bar of 70mm dia is subjected to a pull of 120kN. If E=200GN/m2 and the length is 400mm, calculate:
a) the tensile stress
b) the tensile straing
c) the extension

Any help at all would be appreciated.

 

[Q_Goest]

Can you write down any of the relevant equations? How does stress relate to strain and modulus (E)? If you know strain, and the total length, how would you find extension?