What Temperature Causes a Steel Ball to Loosen in a Pyrex Cube?

[Lance WIlliam]

Homework Statement

A steel ball bearing is encased in a Pyrex glass cube 1.0 cm on a side. At 390K , the ball bearing fits tightly inside the cube.

At what temperature will it have a clearance of 0.90pico meters all around?

Homework Equations

coefficient of linear expansion:
$$\propto$$ =(Change in L / L) / change in T

Im not sure what my Delta L should be...
L= .01 m
T initial is 390K
the $$\propto$$ is 3.2e-6

The Attempt at a Solution

I just need delta L in order to solve for T final

 

[Doc Al]

How does the expansion coefficient of Pyrex compare to that of steel?