the way it bounces
They are usally high compression very low quality two piece balls.
My son and I did this experiment as a science fair project. We put 2 tennis balls in the freezer for 1 hour. We also put 2 tennis balls in heating pad (high setting) for 1 hour. We also used 2 room temperature balls. We dropped the balls from 80" onto a tile floor and measured the height of the bouces with a measuring tape. The results were fairly dramatic. The tennis balls from the freezer bounced an average of 25 inches. The room temperature balls bounced a full 50 inches. The warm balls bounced an average of 55 inches. Obviously there was a significant difference between the bounces of cold and warm tennis balls.
There are many reasons one might choose to purchase a Joola brand of table tennis. The most notable reason being that Joola manufacture's high quality products.
A soaking tennis ball won't bounce high because it has become water-logged
Soccer balls do not go bad. If you purchase a high quality ball it can last for up to a year.
A can of tennis balls is a cylinder. The formula for the volume of a cylinder is V = pr2 h therefore to find the volume: V = p(1.5)2 (8) V=18p
you can go to like dicks sporting goods in Williston Vermont you can get one for at least 100$ for a high quality one but if its not so high its like 20$
Switzerland makes high quality goods from imported materials.
i am not sure but when it gets hot balls tend to expand and preforme like flat balls but when its cold balls usually contract and get tighter and bounce higher.
Cuisenart makes wonderful bread knives. They usually sell their high quality knives in complete sets.
because they need to have a high tensile strength (the maximum stress an object can handle) so the tennis ball is able to bounce of the nylon strings and so the metal frame can stand the tennis balls energy.
On the subject of Fitness balls, I believe that quality much outweighs price. Ball Dynamics is one suggestion (a place to start) for high quality, low burst rate Fitness balls. I think their balls hold up to 600 pounds. Also try about.com/Fitnessballs for some good info before you decide.