Conservation of energy and the 'crazy ball' product Well I'm not sure how many people remember the crazy ball - a small ball made of rubber which bounced like crazy. What I noticed is that the ball seemed to bounce higher than the point from which it was actually dropped. How is this possible? Doesn't this violate the law of energy conservation?
 A: No, it doesn't violate energy conservation, and it doesn't bounce higher than the usual height, if you ''drop'' it (i.e. $v_{\rm initial} = 0$). If you add any force from your side, ''throwing'' it, then it will obviously bounce higher, but still won't violate energy conservation if you include the extra $\frac{1}{2} m v_{\rm initial}^2$ energy it carries at the time of throwing.
The way this process works is this:
The reason why usual balls rebound conspicuously lower than a crazy ball is because they lose energy on impact with the floor - one factor is friction, and another is the loud ''thud'' sound you hear when, let's say, a tennis ball hits the ground. Choice of material matters over here, if you choose a material with a higher coefficient of restitution, you can reduce the amount of energy lost and your ball bounces higher. Now, crazy balls are generally made of synthetic rubber (crudely; more specifically polybutadiene, but how does it matter!) which precisely achieves this. You may have noticed that the thud from a crazy ball is considerably weaker in intensity. 
How all this came about is an interesting story in itself, which you can find here.
While the above reasoning was an intuitive way of stating this, one source where measurements of this effect were made some years back is this article (not sure if you would be able to access and it though, since I don't imagine your school being subscribed to this). 
