Ch0137

# Ch0137 - Chapter 37 The First Law of Thermodynamics 37 The...

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Chapter 37 The First Law of Thermodynamics 266 37 The First Law of Thermodynamics We use the symbol U to represent internal energy. That is the same symbol that we used to represent the mechanical potential energy of an object. Do not confuse the two different quantities with each other. In problems, questions, and discussion, the context will tell you whether the U represents internal energy or it represents mechanical potential energy. We end this physics textbook as we began the physics part of it (Chapter 1 was a mathematics review), with a discussion of conservation of energy. Back in Chapter 2, the focus was on the conservation of mechanical energy; here we focus our attention on thermal energy. In the case of a deformable system, it is possible to do some net work on the system without causing its mechanical kinetic energy 2 2 2 1 2 1 w v I + m to change (where m is the mass of the system, is the speed of the center of mass of the system, I is the moment of inertia of the system, and is the magnitude of the angular velocity of the system). Examples of such work would be: the bending of a coat hanger, the stretching of a rubber band, the squeezing of a lump of clay, the compression of a gas, and the stirring of a fluid. When you do work on something, you transfer energy to that something.

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Ch0137 - Chapter 37 The First Law of Thermodynamics 37 The...

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