Question

A brass plate has a circular hole whose diameter is slightly smaller than the diameter of an aluminum ball. If the ball and the plate are always kept at the same temperature, a) should the temperature of teh system be increased or decreased in order for the ball to fit through the hole? b) Choose the best explanation from among the following:I - The aluminum ball changes its diameter more with temperature than the brass plate, and therefore the temperature should be decreased.II - Changing the temperature won't change the fact that the ball is larger than the hole.III - Heating the brass plate makes its hole larger, and that will allow the ball to pass through.

Answer 1

The temperature should be increased to enlarge the hole in the brass plate, allowing the ball to fit through due to thermal expansion, where both objects and holes in them expand with temperature.

Step-by-step explanation:

The phenomena being described here relates to thermal expansion. Materials tend to expand when heated and contract when cooled. To address the student's question:

• The temperature of the system should be increased to allow the aluminum ball to pass through the hole in the brass plate. This is because both the brass plate and the aluminum ball will expand with heat, but crucially, the hole in the plate will also become larger.
• The best explanation is III: Heating the brass plate makes its hole larger, which will allow the ball to pass through. In general, objects including holes, expand in all directions as temperature increases.

This is due to the kinetic energy of atoms and molecules increasing, which causes them to move apart slightly more, effectively increasing the size of objects and holes alike.