lecture_practiceprobs_sept23

lecture_practiceprobs_sept23 - Introduction The core design...

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Introduction The core design concept for Physics 7A is one that is based on a methodology of problem solving that is called model-based-reasoning. Models have historically been used as a way to propose and predict scientific phenomena. As the technology progresses, experimental methods become more sophisticated and it becomes easier to test theories by directly comparing theoretical predictions to outcomes that are observed and measured through experiment. Models change, progress, and evolve. Sometimes they are fully abandoned in favor of a completely different model that results from experimental outcome. Other times, they are simply modified to more accurately reflect what is experimentally observed. Examples of Models The following are a few examples of models that have been abandoned, or that have progressed and evolved. 1) In the early 1900’s J.J. Thompson proposed the “plum pudding” model of the atom which was later abandoned due to Rutherford’s famous gold foil experiment. 2) Rutherford’s subsequent planetary model was revised by Bohr, who was interested in probing the so-called quantized behavior of the electron energy levels due mostly to spectroscopic observations that suggested this quantization. 3) Most recent models, based on Schrodinger’s equation and the probabilistic behavior of electrons built again on the Bohr mode with substantial revisions. Rutherford, Bohr, and the present day model of the atom are not exclusive of each other, they are progressions of the proposed model by Rutherford, while the plum pudding model has been set aside completely. So the question is: How long does a model work? And the answer is: Until it doesn’t! Models and Problem Solving This introduction to models will help as we set out to understand the first two in a series of very important models that we will use in this class, some of which will be used over and over. Once we understand what they are capable of telling us, we will then begin to use them to make predictions about physical outcomes of specific systems. In other words, we will begin to use them to help us solve problems. And that is of course the position that we started from: solving problems through model based reasoning. The Three Phase Model of Matter Many of us are already familiar with the Three Phase Model of Matter, as it is normally introduced in a high school physical science class. This model suggests that there are three phases to matter; solid, liquid and gas. Most substances can be brought through an entire cycle of solid, liquid and gas, by the addition of energy in the form of heat. As a result, a graphical construct known as a Heating Curve, can be used to describe the phase change phenomena. The take home assignment from your first Discussion/Lab (DL) illustrates a heating curve.
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lecture_practiceprobs_sept23 - Introduction The core design...

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