1-3 IDEALIZED MODELS
we often use the word “model” to mean either a small-scale a model railroad, or a person who displays articles of clothing (or the . In physics a model is a simplified version of a physical system that complicated to analyze in full detail. example. Suppose we want to analyze the motion of a baseball thrown How complicated is this problem? The ball is neither perfectly spherical rigid it has raised seams, and it spins as it moves through the air. Wind and influence its motion, the earth rotates beneath it, the ball’s weight varies a 1 5 i o , from the center of the earth changes, and so on. If we try to include
analysis gets hopelessly complicated. Instead, we invent a simplified We neglect the size and shape of the ball by representing it as a particle. We neglect air resistance by making the ball move in a vacuum, Hearth’s rotation, and we make the weight constant. Now we have a simple enough to deal with. We will analyze this model in detail in idealized model of the system, we have to overlook quite a few minor on the most important features of the system. Of course, we have neglect too much. If we ignore the effects of gravity completely, then that when we throw the ball up, it goes in a straight line and dis ape need to use some judgment and creativity to construct a model that enough to make-it manageable, yet keeps its essential features. a model to predict how a system will behave, the validity of our by the validity of the model. Going back to Galileo once more, we see about bodies corresponds to an idealized model that does not of air resistance. This model works fairly well for a dropped cannon-
for a feather.
idealized models is extremely important in all physical science and we apply physical principles to complex systems, we always use ideas we have to be aware of the assumptions we are making. In fact, the themselves are stated in terms of idealized models we speak about bodies, ideal insulators, and so on. Idealized models player crucial this book. Watch for them in discussions of physical theories and their specific problems.