Calculating Tension of Steel Wire at Different Temperatures

[HWManiac]

Here is the problem:

A steel wire of a radius of 6E-4 is stretched between two concrete blocks. When the concrete and the steel are at 65degreesC the steel has a tension of 100N. what is the tension of the steel at 200degreesC?

I started the problem with using youngs modulus of:

Stress = (F/A) = Y(alpha)(delta T)

When I finished the problem i got a really small tension.

Any suggestions? (Don't just tell me the answer.)

 

[gnome]

I don't think elasticity is the issue here.

Try coefficient of linear expansion.

Keyword = thermal.

 

[HWManiac]

After using the coefficient of linear expansion then do i use youngs modulas?

 

[gnome]

You use both together.

Young's modulus will let you get an expression for the change in length due to strain, in terms of L_i.

The coefficient of expansion will give you an expression for the change in length due to thermal expansion.

Putting them together should give the new tension.

Only trouble is, when I do it, I end up with the wire under a compression force of 236 N, not tension. Seems to me that the thermal expansion is more than 3 times as great as the original stretching due to the tension. But maybe I made a mistake somewhere. [?]