Modeling Physics in Javascript: Gravity and Drag

This is the first post in the Modeling Physics in Javascript series. As such, we'll need to cover some introductory material. There are some of you who have real training in physics and calculus. You may be tempted to scream "that's not the whole story" at me when I explain some concepts, and my response to you is this: I wish I could cover all the amazing parts of physics and calculus in one blog post, but I can't. I'll therefore cover only the bits I need. Hopefully, the people reading this will accidentally learn physics while trying to pick up some cool JS tricks.