How does temperature affect the expansion of steel railway track?

[martinbandung]

https://drive.google.com/file/d/0Byoif068nH-zbk8tVmhCQVlYMlk/view?usp=drivesdk
1. Homework Statement
The steel railway will be constructed in a place that temperature can change 8°C. Length of each rail is 10 m. With α=11*10^-6 . Minimum space required between the rail is...

Homework Equations

ΔL= L0 α Δt

The Attempt at a Solution

I confuse wether i should multiply it by 2 or not. Where does the expansion go (direction). Is it only to one or two direction (left or right)?

Picture https://drive.google.com/file/d/0Byoif068nH-zbk8tVmhCQVlYMlk/view?usp=drivesdk

 

[haruspex]

Where does the expansion go (direction). Is it only to one or two direction (left or right)?

The expansion does not have a direction unless you nail one end in place. It is just a change in overall length.

 

[CWatters]

I confuse wether i should multiply it by 2 or not. Where does the expansion go (direction). Is it only to one or two direction (left or right)?

Apply the same rule to the sections of track either side of the one you are considering. You will find it makes no difference...

If it goes "one way" then the increase in length encroaches into one gap (the other end is fixed).

If it goes two ways half the increase in length encroaches into two gaps (one each end) but then the same applies to the sections either side. So again one increase in length encroaches into one gap.