The concept of work

The concept of work is developed here from an operational point of view. Mechanical work is discussed first, and then the concept is expanded to more-general interactions. Observation shows that there are actions that, when acting on a body cause a change in the velocity of the body. Such actions are called forces. The relation between the force and the change of velocity is expressed by Newton s second law of motion ... 

We return to the piston-and-cylinder arrangement discussed in Section 2.3. In that discussion we did not completely describe the process because we were interested only in developing the concept of work. Here, to complete the description, we choose an isothermal process and a gas to be the fluid. We then have a gas confined in the piston-and-cylinder arrangement. A work reservoir is used to exert the external force, Fe, on the piston this reservoir can have work done on it by the expansion of the gas or it can do work by compressing the gas. A heat reservoir is used to make the process isothermal. The piston is considered as part of the surroundings, so the lower surface of the piston constitutes part of the boundary between the system and its surroundings. Thus, the piston, the cylinder, and the two reservoirs constitute the surroundings. 

In Chapter 2, we pay a renewed visit to thermodynamics. We review its essentials and the common structure of its applications. In Chapter 3, we focus on so-called energy consumption and identify the concepts of work available and work lost. The last concept can be related to entropy production, which is the subject of Chapter 4. This chapter shows how some of the findings of nonequilibrium thermodynamics are invaluable for process analysis. Chapter 5 is devoted to finite-time finite-size thermodynamics, the application of which allows us to establish optimal conditions for operating a process with minimum losses in available work. 

This problem involves the concept of work, so a good equation to start with is W = F d. To apply this equation we must obviously know the magnitude of some force and the magnitude of a displacement. The distance is 0.020 m, but what is the force Three key words in this particular problem are 100 kg patient. Since the patient has mass, the patient has a weight, which is a force. Using W = m g, we can readily calculate the patient s weight ... 

This problem also involves the concept of work, so a good equation to start with is still W = F d. Note that we must consider the mass of both the patient and the operating table. A complete reading of the problem will yield some very valuable information. The object to which the force is being applied, the patient on the table, does not move. Therefore, d = 0 m and the work done is 0 J. 

This problem involves the concept of work done on or by a gas under constant pressure conditions thus we can use W = P AV. In order to end up with SI units, we need to convert everything to SI units. Examining the data, we see that liters are not official SI units and must be converted to the official SI unit of volume, m3. There are 1000 L in one cubic meter. 

Now we examine the amount of work the cell performs under various conditions. To help understand the concept of work of a cell, the case of gas expansion in a cylinder is reviewed below ... 

The concept of heat, q, being transferred is a familiar experience. In contrast, the concept of work being done, w, (in the thermodynamic sense ) is relatively unfamiliar. 

Baddeley A. 1981. The concept of working memory A view of its current state and probable future development. Cognition 10 17-23. 

The concept of "work functions, " the values of which are either equal to or derivable from the above energetic factors, are used below. These lend themselves more readily to considerations of mechanisms and kinetics. 

We furnish one example to illustrate further the concept of work. Consider a mass M attached to the end of a weightless spring, as shown in Fig. 1.5.5. Initially the system of (mass + spring) is at equilibrium when no net force acts of the... 

This law of the conservation of energy makes it easy to understand the concept of work in a physical system, but it is not immediately obvious that work and energy are factors in chemical reactions too. Consider, however, the combination of carbon and oxygen to give carbon dioxide. We write the equation... 

For experimental chemistry it is easy to visualise heat being transferred to a reaction flask, e.g. by heating. The concept of work done on a chemical system is more difficult to visuaUse. However, for the purposes of this book there are three types of work which have to be considered ... 

The concepts of work and of heat are of fundamental importance in thermodynamics, and their definitions must be thoroughly understood the use of the term work in thermodynamics is much more restricted than its use in physics generally, and the use of the term heat is quite different from the everyday meaning of the word. Again, the definitions are those given by J. A. Beattie. ... 

The concept of work is one that is familiar in the discipline of mechanics. We shall, of course, utilize the same concept here but shall consider some aspects not emphasized in mechanics. Work is defined as the line integral of a generalized force over a generalized path. Consequently, the differential element of work is... 

De Berg, K. C. (1997). The development of the concept of work A case where history can inform pedagogy. Science Education, 6, 511-527. 

The concept of working arenas can help you divide up work in ways that include but go beyond the formal job-department-function-business model. It frees you to ask a critical series of six questions that make it easier to apply performance-based outcome gotils, including ... 

The path to the concept of work leads through many steps (Fig. 2.2). The quantity called force is also defined indirectly (force = mass times acceleration). The same holds for acceleration (= change of velocity divided by time interval) as well as velocity (= distance covered divided by time needed to cover it). Mechanical work is only one form of energy input. There are other forms as well, the most... 

The equation F = m -a is usually used to define the force F, which is then used to introduce the concept of work and, as a generalization, energy (compare Sect. 2.1). 

Students often confuse the concept of work with power. Power represents how fast you want to do the work. It is the time rate of doing work, or said another way, it is the work done divided by the time that it took to petfisrm it. For instance, in Example 10.16, if we want to lift the box in 3 seconds, then the power required is... 

In Section 13.1, we reviewed the concept of work as presented in Chapter 10 and explained the different forms of eneiggr. now consider what is meant by the term power. Power i for-... 

Intimately linked to the concept of work function is the process of thermionic emission. Thermionic emission is, as the name suggests, the phenomenon whereby electrons are ejected from a metal when it is heated in vacuum. The electrons that require the least amount of thermal energy to overcome their binding energy in the solid and... 

The above provides some insight into the interpretation of the concepts of work and heat at the molecular level, which up to now has eluded our grasp. Let us write out the expression for the energy of the system in terms of its various different energy levels as indexed by i E = Now consider an... 

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