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### Introduction to Physics

For some reason, there is a common fear or unapproachable feeling about physics. When I was in college and the fact that I was a physics major came up in conversation, I would inevitably get one of three odd looks. The first one implied that I had just sprouted another head; the second made the person appear to have gotten a sour taste in his or her mouth; the third (my favorite) was a consoling glance that said “I am so sorry.” I'm not sure what caused this general feeling about physics (hey, my physics-lab buddies and I were really fun guys!), but rest assured that in this chapter we will allay those fears.

Physics is the branch of science that studies and describes the behavior of objects in nature on the most fundamental level. Here are some interactions and occurrences that physics is used to describe:

• An object falling to the ground (remember Isaac Newton and his apple)

• The effect of an electron on a proton

• Electrical current

• The motion of the planets

There are many fields of specialized study within physics, and some areas of physics are very difficult to learn. Fortunately for us, Flash requires us to learn only the basics of the easiest-to-learn type: classical mechanics. Classical mechanics is the one area of physics where it is easy to conceptualize what is happening, or what should happen, in a simple situation. For instance, if you have a ball on a hill, you don't need an advanced degree in science to tell you that the ball will roll down the hill—common sense should suffice. (In other areas of physics, it can be difficult to predict what will happen just by looking at the situation.)

In this chapter we will discuss the basic concepts of speed, velocity, and acceleration; Newton's laws; gravitation; and friction. We will not cover conservation of energy or of momentum until Chapter 6, “Collision Reactions.” This is because we are trying to introduce topics and concepts in a somewhat linear fashion. Conservation of energy and momentum are concepts that apply after there has been a collision of objects, and we have not yet reached that point.

One more thing to note before we jump in: I'm going to be making some distinctions between real physics and good-enough physics. Real physics concerns the motion and reactions that can be described by real physics equations. Everything initially discussed in this chapter is real physics. However, there are situations where the real physics equations may be a little too intense for Flash to calculate frequently. As it turns out, they can be replaced with vastly simplified equations that give good-enough results. We will discuss two of the most commonly used “good-enough” physics substitutes in the “Gravity” and “Friction” sections.

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