2. An aluminum plate has a circular hole cut in it. A copper ball (solid sphere) has exactly the same diameter as the hole when both are at room temperature, and hence can just barely be pushed through it. If both the plate and the ball are now heated up to a few hundred degrees, the ball will fit more easily. Why

Thermal expansion

Explanation:

One of the effects of heat is that it causes expansion of materials.

When the copper ball and aluminium plate are both heated, the both materials expand. When they expand, the copper ball can is found to fit more easily into the aluminium plate after both metals have become wider than they were at room temperature.

The coefficient of thermal expansion for aluminium is 35% greater than that of copper. This is the reason why the copper ball can fit into the aluminum plate more easily at higher temperature. The aluminum has expanded 35% more than copper making it easier and leaving a lot of space for the copper to fit into the aluminum plate.