How do you determine strain and stress of a spring when given force, length, and change in length?
http://www.efunda.com/DesignStandards/springs/calc_comp_Fstress.cfm
This is a calculator to do it, sheer stress is actually a complicated thing, as you see.
I am wondering if your teacher means for stress to just be force applied? It is not the meaning of stress, but ...
http://www.efunda.com/DesignStandards/springs/calc_comp_Fstress.cfm