Re: Wouldn't expansion and contraction help me out?

Hello.  

This is a classic physics experiment. Heating and cooling causes more than 
just expansion and contraction, and your experimental data points this 
out.  In addition to volumetric changes noticed when heating and cooling 
(expansion/contraction), many physical properties change as well, such as 
hardness and resiliency.  This material property change with repect to 
temperature affects each of your ball types differently.  The key is to 
not to expect the same change in properties for all of the balls because 
the materials and methods of construction are not the same. For example, 
the baseball and softball have similar leather covers, but inside those 
covers they are very different.  

Your bounce test at the various temperatures bear this out.  The same is 
true for the other types of balls in your group.  They are all affected 
differently by the various temperatures.  In some cases there is very 
little if any change in rebound due to temperature, and in other cases 
there is a signifigant change in rebound due to temperature.  Try to 
seperate the balls into groups and determine how the temperature changes 
affect each group.

Good luck
Greg