@134318c2 The thing is, they took away a lot of those practical examples in modern mathematics courses - which is why you get so much "what is this good for?" these days. Nothing does for the dx/dt velocity stack like ballistics. 

 @ed87129f 

What is it good for? It tells you how to set up the machine correctly so that you hit the bastards. 

LOL.

Why does it work? What a stupid question. Memorize the next chapter. 

It's a mixed bag.