(adsbygoogle = window.adsbygoogle || []).push({}); youngs modulus....

there are two rods rod1 , made of brass - length L1=2m

area of cross section A1 2x10^-4 m^2 and young's modulus y1= 10^11

rod 2 , made of steel , lenght L2 , cross sectional area A2=10^-4 m^2 and youngs modulus y2 = 2x10^11 .

the question is if the two rods are fixed end to end , and two equal and opposite forces are applied at each end (the ends not fixed to each other-free ends )pulling the combination of both the rods outward,

and the value of the forces applied are 5x10^4 on both sides.

then find the length of rod 2 such that both have equal increase in length dl (read delta L ) as a result of the forces.

here's what i did ,

i assumed that because both the rods are fixed at one end , any extension that takes place will occur in the direction of the force

i.e F = (y1.A1.dl)/L1

i know F,A1,y1,L1 theredore i can find dl

now i substituted this dl in the corresponding equation for rod 2 and then found L2 ( F=( y2.A2.dl)/L2 )

and i got it to be equal to 2m but the answer in the solutions given out was 1.8m

i want to know what is wrong with my assumption because i am sure something is wrong with it...

or if take the lenght of the total rod to be L1+L2 i.e L2+2and take the midpt. of the rod as the origin for calculating ..

oh well i'm very confused..

please help me if u can!

thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Youngs modulus

**Physics Forums | Science Articles, Homework Help, Discussion**