What are the Stress and Strain in each rod?

[thetruth1988]

Homework Statement

A copper rod of 2 meters is joined to a steel rod with length (ls) and with cross sectional area of 1.0cm² and 2.0cm² respectively the compound rod is subjected to an equal and opposite force of 3x10⁴N.
Find:
a) The length of the steel rod if the elongation of the steel rod is equal.
b) What are the stress and strain in each rod?

Homework Equations

The modulus of copper : 1.0 x 10'' N/m²
The modulus of steel : 2.0 x 10'' N/m²

The Attempt at a Solution

I just want to be honest guys.., I have not tried any solutions because I really don't know where to start. please help me

 

[tiny-tim]

Welcome to PF!

Hi thetruth1988! Welcome to PF!

A copper rod of 2 meters is joined to a steel rod with length (ls) and with cross sectional area of 1.0cm² and 2.0cm² respectively the compound rod is subjected to an equal and opposite force of 3x10⁴N.
Find:
a) The length of the steel rod if the elongation of the steel rod is equal.
b) What are the stress and strain in each rod?

(Do you mean "if the elongation of the steel rod and the copper rod are equal" ?)

Hint: what is the elongation of the copper rod under an equal and opposite force of 3x10⁴N ?

Then what is the elongation of the steel rod under the same equal and opposite force, if the length of the steel rod is L ?

 

[thetruth1988]

F_steel = (E_steel A/L) ΔL_steel

omg! sorry.., I really don't know what to do.. :'( can you help me out with an equation?

 

[HPRF]

This looks like a question were you should use Youngs Modulus. Look that up and use it; it should solve the problem...