| Basic Thermodynamics ~ J. Pohl © | www.THERMOspokenhere.com (9-A116) |
The beginning ideas of Isaac Newton regarding mechanics form the foundation of engineering thermodynamics. These topics are taught in high school physics but without vectors, calculus or differential equations. The following is an overview of HS physics which includes the mathematics Newton invented because he needed it. Also some terminology evolved since Newton is introduced.
The first definition or axiom of Newton's Laws of Motion defines mass as a measurable property of matter.
Axiom I: The quantity of matter is the measure of the same, arising from its density and bulk (volume) conjointly.
The equational relationship of a mass to its density and volume is:
| (1) 1 |
System: The typical procedure of any analytic analysis of physical reality begins with selection of a system and a system model. The system is matter. It is matter (of all of matter) most directly associated with the event (or non-event) of interest.
Model: (or system model) The physical matter of an analysis is an approximation of the matter of the actual system. Approximation might be for the sake of expedience. More often, due to complexity of the matter, approximation is a necessity.
For his Laws of Motion, Newton made virtually no use of the fact that mass has the factors, density and volume. The focus of his laws was simply some mass, a mass or . It is clear that his "quantity of matter" was, as we would call it today, his system. Newton attempted to study reality and its events "at the basis" meaning in the smallest sense, in the slightest of occurrence. Thus the masses of his rationalizations had measurable mass but were "vanishingly small" in size. This amounts to a model: the BODY.
BODY When an amount of real physical matter is selected for study, and modeled (approximated) as having its mass located "at a point," the model is called a BODY. More will be said about Newton's ideas later, as needed. For now the simple idea of BODY as his system is what we need.
Actual systems, amounts of matter we might model for analysis as a BODY are difficult to visualize. More commonly the systems we encounter have extent. They have a distribution of matter over the space they occupy and a density (or effective density). Automobiles, boxes, logs, to name a few, are matter distributed over the space they occupy. Nonetheless, it is so convenient to model these systems as having their masses "at a point." Thus a new model will arrive for such analyses. It is called an EXTENDED BODY.