摘要:

Mixing processes exist with positive entropy change and negative free energy change. However, the idea that theirreversibilityof the mixing processes is responsible for the so‐called free energy and entropy of mixing is faulty. The mixing, as well as the demixing processes may be associated with either reversible or irreversible phenomena, depending on the particular conditions. For ideal gases, the word ‘‘mixing’’ in the terms ‘‘mixing entropy’’ and ‘‘mixing free energy’’ may sometimes be useddescriptivelybut nevercausatively. The quantity −∑NiR ln Xi, usually referred to as ‘‘mixing entropy,’’ has nothing to do with the mixing phenomenon. Therefore the terms ‘‘mixing entropy’’ and ‘‘mixing free energy’’ are essentially misconceptions. In fact, it is shown that the process of mixing of ideal gases has, by itself, no relevance to any thermodynamic quantity. Therefore, in a thermodynamical sense, it is a nonprocess. The concepts of assimilation and deassimilation are introduced. It is shown that the ‘‘deassimilation process is essentially irreversible.’’ This should replace the traditional principle that ‘‘the mixing process is essentially irreversible.’’

ISSN:0002-9505    

DOI:10.1119/1.15064

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

A two‐dimensional flame table was constructed for visually demonstrating acoustical modes in a cavity. This flame table is an extension of the one‐dimensional flame tube or Rubens flame tube apparatus. Photographs of some of the lower‐order modes on rectangular box and cylindrical box flame table cavities are included.

ISSN:0002-9505    

DOI:10.1119/1.15030

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

It is pointed out that the usual treatment of the delta function potential in the one‐dimensional Dirac equation is incorrect. Steps leading to such incorrect results are identified. The delta function potential is also examined from the limiting case of a nonlocal potentialV(x,x’). In this general case, the strengthg=∫dx ∫dx’V(x,x’) is no longer a sufficient parameter to characterize a potential.

ISSN:0002-9505    

DOI:10.1119/1.15031

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

Relativistic mass is discussed in both a pedagogical and historical context. It is pointed out that its introduction into the theory of special relativity was much in the way of a historical accident. Gaining widespread use initially in instruction, the use of relativistic mass is showing signs of progressive disfavor. An analysis and criticism of the various ways relativistic mass is used in relativity is detailed and special attention is given to the frequent misuse of relativistic mass as an inertia.

ISSN:0002-9505    

DOI:10.1119/1.15314

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

Gantmakher’s formula for the Coriolis deflection of a point mass moving in a uniform gravitational field is derived by vector methods. The results for the eastward deflection of a falling object and the lateral deviation of a horizontally fired projectile are derived as special cases of this formula. A homogeneous variant of Gantmakher’s formula is shown to yield the rotation formula describing the change in a vector rotated through a finite angle about a fixed axis. The motion of a point charge in constant uniform electric and magnetic fields is also shown to be solved by Gantmakher’s formula.

ISSN:0002-9505    

DOI:10.1119/1.15033

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The role of entropy change as the basic cause of the restoring force in a piece of stretched rubber has been understood for some time. The less‐utilized kinetic view, in which the restoring force is the time average of the dynamical forces due to the interaction of thermal motion and the covalent constraints, provides a clearer physical picture. The equivalence of the two viewpoints is demonstrated.

ISSN:0002-9505    

DOI:10.1119/1.15034

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15036

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15037

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15038

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15039

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP