# Need help on Thermal Expansion problem

A brass ring of diameter 10.00 cm at 20 degrees Celsius is heated and slipped over an aluminum rod of diameter 10.01 cm at 20 degrees Celsius. Assuming the average coefficients of linear expansion are constant, a) to what temperature must this combination be cooled to seperate them? b) What if the aluminum rod were 10.02 cm in diameter?

I don't know where to start for this problem. Any help will be much appreciated. Thx in advance!

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Tide
Homework Helper
Start by looking up the thermal expansion coefficients for aluminum and brass!

Ok. So far I know that the average coefficient of linear expansion of aluminum is 24*10^-6 and brass is 19*10^-6. I have this equation:
$$\Delta L=\alpha L_{i}\Delta T$$
where $$L_{i}$$ is the initial length. I don't understand how to apply this equation to the two materials.

Last edited:
Tide
If a material starts off with length (diameter) $L_0$ then its new length, after a temperature change, will be $L = L_0(1+\alpha \Delta T)$.