Thermodynamics

Thermodynamics States About Energy Conversion Thermodynamics is the branch of science that embodies the principles of energy transformation in macroscopic systems. The general restrictions which experience has shown to apply to all such transformations are known as the laws of thermodynamics. These laws are primitive; they cannot be derived from anything more basic. The first law of thermodynamics states that energy is conserved; that, although it can be altered in form and transferred from one place to another, the total quantity remains constant. Thus, the first law of thermodynamics depends on the concept of energy; but, conversely, energy is an essential thermodynamic function because it allows the first law to be formulated. This coupling is characteristic of the primitive concepts of thermodynamics. The words system and surroundings are similarly coupled. A system is taken to be any object, any quantity of matter, any region, and so on, selected for study and set apart (men

Graphic Representation of a Force

Although it is possible to describe a force by using words alone, the easiest and clearest method of describing a force is by means of a diagram. Like on the picture below, each of the forces represented, the straight line l indicates the position of the line of action of the force with respect to the body 2 on which the force acts, and the arrow head indicate the direction of the force along its line of action.


The arrowhead may be placed at one end of the line of action or at some convenient point on the line of action. The magnitude of each force is the number of the pounds shown, and the length of the line of action is chosen arbitrarily. In some diagram constructed for solving problems, the relative magnitude of two or more forces are indicated by the lengths of specific segment of lines that are drawn parallel to the lines of action of the forces. In (d), the line of action of the force is inclined at the indicated angle with the horizontal, and the force tend to pull body to the right.

In (a), the line of action of the force is horizontal and the force acts towards the right along the line of action. In (b), the line of action of the force is vertical, and the force acts downward along its line of action. The line of action of the force in (c) is inclined to the horizontal at an angle equal 30o and the force tends to push the body to right.

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