# Homework Help: I need help here

1. Dec 7, 2009

### Dr.Wasim

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

A steel rod 4.00 cm in diameter is heated so that its temperature increases by 70.0 C. it is then fastened between tow rigid supports. The rod is allowed to cool to its original temperature. Assuming that Young's modulus for the steel is 20.6 * 10^10 N/m^2
and that its avarege coefficient of linear expansion is 11 * 10^-6 1/C , Calculate the
tension in the rod.

2. Relevant equations

Delta L = L1 * alfa ( avarege coefficient of linear expansion ) * delta T

and

F / A = Y delta L / L

3. The attempt at a solution

I found delta L / L from first law above

then i found tension from second law

Best wishes for you

2. Dec 7, 2009

### Dr.Wasim

today the last time for answer

3. Dec 8, 2009

### Redbelly98

Staff Emeritus

4. Dec 8, 2009

### Dr.Wasim

But i doubt in my method because the rod's length will decrease by cooling

and it will exert force on supporter

and my equation for solution contain avarege coefficient of linear expansion

not for compression .... understand me ?

5. Dec 8, 2009

### Redbelly98

Staff Emeritus
The coefficient of expansion applies equally to the case of cooling/contraction.