Mass

The earlier chapters of the book have gone into several aspects of motion: velocity, acceleration, vectors, friction, bouncing, easing, springing, and gravity. One thing that I have pretty successfully gotten away with ignoring is the concept of the mass of the object being moved around. Now, Im going to reissue my standard disclaimer here, and say that there are probably several points in the book so far where, scientifically speaking, mass should have been in the equation. But Ive generally concentrated on doing things mostly correctly, and kept the emphasis on making sure it looks right. Most important, the final result must be efficient enough that it wont totally kill Flash in the process.

Unfortunately, or maybe fortunately, I have reached a point where I just cant ignore mass any longer. Mass is just so tied up in the subject of momentum that Im just going to have to confront it head on.

So just what is mass? Here on earth, we usually think of mass as how much something weighs. And thats pretty close, as weight is proportional to mass. The more mass something has, the more it weighs. In fact, we use the same terms to measure mass and velocity: kilograms, pounds , and so on. Technically speaking though, mass is the measurement of how much an object resists change in velocity. Thus, the more mass an object has, the harder it is to move that object or to change how that object is moving (slow it down, speed it up, or change its direction).

This also relates to acceleration and force. The more mass something has, the more force you need to apply to it to produce a given acceleration. The engine in my Chevy Cavalier is designed to produce enough force to provide reasonable acceleration on the mass of a Chevy Cavalier ( barely ). Its not going to produce enough force to accelerate a large truck. The engine would need a lot more force, because the truck has a lot more mass.