A brass plate has a circular hole whose diameter is slightly smaller than the di
ID: 1463125 • Letter: A
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 the system be increased or decreased in order for the bal 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.
Explanation / Answer
Aluminium thermal expansion coefficient is 23.1 part per million per degree K, while for brass it is 20.3.
Cool the system and the hole in the plate will get smaller at a faster rate than the brass ball shrinks, eventually to a point where the hole will be smaller than the ball.
Therefore correct answer is:-
I. The aluminum ball changes its diameter more with temperature than the brass plate, and therefore the temperature should be decreased.
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