Temp problem

1. Jan 31, 2004

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.)

Last edited: Jan 31, 2004
2. Jan 31, 2004

gnome

I don't think elasticity is the issue here.

Try coefficient of linear expansion.

Keyword = thermal.

3. Jan 31, 2004

HWManiac

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

4. Jan 31, 2004

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 Li.

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. [?]