Finding Young's Modulus

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1. Jul 8, 2015

toforfiltum

1. The problem statement, all variables and given/known data

2. Relevant equations
E= (F/A) x (L/ΔL)

3. The attempt at a solution
I know that since the material is the same, the Young modulus should be the same. However, when I try to find the ratio of the second wire to the first, I get the answer C. For the first wire, E= 4FL / d2Δl, since A = d2/4.
For the second wire, the value of E I obtain is F x ½L / (d2/16) x Δl , which is twice the first value. I can't see what's wrong with my working. Can someone point it out?

2. Jul 8, 2015

vanoccupanther

This is a conceptual question, so we know for a particular material at a certain temperature Young's modulus will be a constant. Using the above equation we see that area does not reduce linearly so you're probably wondering how do I compare a thicker wire to a thinner one. Remember that to get the same ratio of change in length from original length in the thinner wire will require less force. So while your area is a quarter of the size of the original wire, the force needed is also reduced.

3. Jul 8, 2015

toforfiltum

Oh I see, so from the information given in the question above, there's no way of obtaining the same value of E as the first wire without knowing the change in the value of F is it?

4. Jul 8, 2015

vanoccupanther

Yes, its not meant to be solved numerically.

5. Jul 8, 2015

Ok, thanks.