Happy Unhappy Balls - Happy Sad Balls

The difference between the balls is striking, and it makes an outstanding visual demonstration. The properties of the "sad" ball are so different from what you would expect, even my co-workers, who are engineers, were surprised. I love to see the looks on their face! This is a great material demonstration.

Great product

These are about 1 inch in diameter, perhaps a little smaller. The high hysteresis ball is amazing...zero bounce. They do have a slightly different finish between the two, but the quality is good (better than Amazon I would guess). I used them for a demonstration of rolling resistance. The low hysteresis ball rolls twice as far down an incline.

Great Balls of Rubber!

Everyone enjoys these and they help engage a conversation about materials and the science behind them. One person who follows Formula One racing mentioned to his son that these are similar to the differences between soft and hard tires which the racers need to choose carefully depending on conditions.