Energy Transfer

So I didn't have a picture of this one. Instead, I got it from http://eisforexplore.blogspot.com/2012/03/energy-transfer-for-kids.html, although I searched for it after planning my post.

When you drop a tennis ball placed on top of a basketball, the tennis ball bounces higher than it does when dropped alone, and the basketball does not bounce as high. When trying to understand this, take into account the energy transfer that takes place when the two balls come into contact. As the basketball begins to rebound, it hits the downward-falling tennis ball, thereby transfering some of its (the basketball's) energy to it (the tennis ball). For this reason, the basketball has less energy and therefore attains a lower height, while the tennis ball gains altitude.