# Linear Thermal expanion what is the formula we use?

1. Dec 13, 2009

### Idrees

Linear Thermal expanion!! what is the formula we use???

1. The problem statement, all variables and given/known data
I have been given a linear coefficient which 1.2*10^-5 of something
i have been given the initial temperature of 30 degrees and final temperature of 55 degrees
I have been given that initial lenght is 3.0 m

I am trying to find the unknown final lenght ?????

2. Relevant equations
please whats the relevant equation i need to use

3. The attempt at a solution

2. Dec 13, 2009

### rock.freak667

Re: Linear Thermal expanion!! what is the formula we use???

try $extension=L\alpha T$

3. Dec 13, 2009

### Idrees

Re: Linear Thermal expanion!! what is the formula we use???

im sorry which one is extension

i used one forumula and i got 50

it was Final lenght= a Lenghts (final temp -initial temp) + initial lenght
thus final lenght = 2.0 m (initial lenght) *( 45 deg-20 deg) + 2.0 m
= 50 meters

is this right approach ????

4. Dec 13, 2009

### rl.bhat

Re: Linear Thermal expanion!! what is the formula we use???

In then problem the initial length is 3 m.
The relevant equation is
Lf = Li( 1 + alpha*change in temperature) where alpha is the coefficient of linear expansion.

5. Dec 13, 2009

### Idrees

Re: Linear Thermal expanion!! what is the formula we use???

thank you for that