system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do bouncy balls bounce so high?
gpt
Let us imagine the perfect bouncy ball. A feature of it will be that if you drop it at any height, it will bounce up to about the height your dropped it. It will not bounce any higher than the initial drop unless you put in extra energy somewhere as energy cannot be created or destroyed, it can only be transformed into different types.

Now imagine you take a hackey sack and drop it from the same height. It doesn't bounce up at all. 

Now imagine a steel ball and doing the same thing. It bounces up, but not very high.

What is the differences between all these cases? Well, it is energy transfer. When you drop a bouncy ball, it gains kinetic energy during the fall, and when it hits the ground and reverses direction, very little of the kinetic energy is lost. On the other hand with the steel ball, we know that since it is not reaching the same drop height that some of the energy is going somewhere. It usually converts into heat, but there could be something else at play.

Bouncy balls bounce so high because the material they are composed of doesn't easily convert kinetic energy into other types upon bouncing. Other materials don't bounce so high or not at all because they convert a lot of kinetic energy into other types of energy.