What are the Stress and Strain in each rod?

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Homework Help Overview

The problem involves a compound rod made of copper and steel, subjected to a force, with the goal of finding the length of the steel rod and determining the stress and strain in each rod. The context is rooted in material mechanics, specifically focusing on the concepts of stress, strain, and Young's Modulus.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster expresses uncertainty about how to begin solving the problem. Some participants clarify the conditions regarding the elongation of both rods and suggest considering the elongation of the copper rod under the applied force. Others mention the relevance of Young's Modulus in approaching the problem.

Discussion Status

The discussion is ongoing, with participants providing hints and guidance without reaching a consensus. There is an acknowledgment of the need to apply Young's Modulus, and some participants are exploring the implications of equal elongation in both rods.

Contextual Notes

The original poster has not attempted any solutions and is seeking foundational help, indicating a potential lack of understanding of the underlying principles of stress and strain.

thetruth1988
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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
 
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Welcome to PF!

Hi thetruth1988! Welcome to PF! :wink:
thetruth1988 said:
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 ? :smile:
 
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?
 
This looks like a question were you should use Youngs Modulus. Look that up and use it; it should solve the problem...
 

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