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loudgrrl4_ever

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If the elastic limit of copper is 1.50E8 N/m2, determine the minimum diameter a copper wire can have under a load of 10.5 kg if its elastic limit is not to be exceeded.

Obviously I am looking for d in this problem. I am given the downward force (102.9 N = ma); A = (pi * d2)/4.

I am having trouble identifying the correct symbol for the elastic limit. My professor has a habit of hading out worksheets full of formulas with no explanation on them. For some reason I know that when given modulus, it will be called modulus, so this is the TSmax? I'm quite confused.

Trying it with 1.50E8 = stress, I get stress = F/A; A = F/stress; (pi/4)d*d = F/stress; d = (sqrt)[(4*102.9)/(pi * 1.5E8)]; d=.000934m; d=0.93400mm

If I knew the unit strain, or the length and change in length this problem would be much easier. I haven't done any with so little information before.

I haven't tried that answer yet (I just checked and I answered 0.093400 earlier when I thought I used this) but I would just like to know that I have done it correctly. My textbook spends all of a page and a half talking about this section, and it makes little sense to me unless the problems are simple.

Any help you can give towards understanding this section of Physics would be very helpful and appreciated (especially links/explanations).

Thanks :)