Question

A brass disc fits snugly in a hole in a steel plate. Should you heat or the system to loosen the disc from the hole ? Given that ${\alpha }_B>{\alpha }_{Fe}$.

Answer 1

On cooling, both the radius of hole and brass plate will decrease. But since ${\alpha }_B>{\alpha }_{Fe}$, decrement in the radius of brass disc will be more than that of steel hole and hence the disc will loosen.