# Homework Help: Tension in string attached to two fixed points

1. Dec 14, 2004

### fluz

I'm having trouble with this physics problem:

A piece of steel wire (diameter 2mm) is connected between two fixed points. The tension in the wire is 120N at 0 degrees Celcius. At what temperature is the tension 0?

I assume that I first have to calculate how much "too short" the string is (thus creating tension), and after that calculate how much the temperature has to rise for the wire to expand that much.

My problem is that I don't know how the wire length relates to the tension. Can someone point me in the right direction, please?

2. Dec 14, 2004

### Andrew Mason

This looks like a Young's Modulus problem:
$$\lambda = \frac{T/A_{wire}}{x/L_{wire}}$$

You can work out the ratio x/L from the tension if you look up Young's modulus for steel. Then work out the temperature that would cause the string to expand that amount.

AM

3. Dec 14, 2004

### hhegab

Andrew Mason, you are just smart!

hhegab