ISSN:0002-9505    

DOI:10.1119/1.10535

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

Between 1796 and 1824, Laplace published five forms of his theory of the origin of the solar system—a fact ignored in the literature on Laplace and cosmogony. Yet, those five forms not only reveal Laplace’s undue fondness for his theory, but also give a glimpse of his biased handling of recent discoveries in astronomy and of his reluctance to test in a quantitative manner some grave dynamical problems implied in his theory, later called the nebular hypothesis.

ISSN:0002-9505    

DOI:10.1119/1.10539

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

This report is concerned with the evaluation of two methods of instruction and the two procedures for assigning students to these methods, which were used in a physics course at Cornell University. The report analyzes student achievement and student attitudes.

ISSN:0002-9505    

DOI:10.1119/1.10153

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

A three‐year general physics major has been in operation for five years. It uses a single text from which a sequence of three one‐year courses has been constructed by using a modified spiral approach. Laboratory work is required in each course, culminating in an experimental project during the sixth semester. The advantages gained are unity of presentation and economy of time. This economy benefits the physics staff; it also benefits the students by permitting a wider election of courses. The three‐year sequence can be entered directly by well‐prepared freshmen or preceded by a college‐level introductory course. A special program during the opening of the fall semester helps freshmen to choose between the two options.

ISSN:0002-9505    

DOI:10.1119/1.10154

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

An induction motor is modified to allow its housing (H) and its armature (A) to rotate freely and independently about their common axis. When an alternating potential difference is applied, H and A start rotating in opposite directions, which suggests conservation of angular momentum; this is quantitatively verified by finding that no torque is required to tilt the direction of the axis of rotation. If, however, either H or A is prevented from rotating, a considerable torque is required for tilting.

ISSN:0002-9505    

DOI:10.1119/1.10156

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

Physical systems containing phase information may yield subtle discrepancies in their analysis if complex variables are manipulated carelessly. Modern Fourier transform methods discourage numerical hand‐checking of computer outputs, with the result that errors in handling phase can easily escape detection. An illustration of this possibility is drawn from the field of Fourier spectroscopy, but the applicability is much wider.

ISSN:0002-9505    

DOI:10.1119/1.10157

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

Three different sets of analytic wave functions are used to calculate the Na(3s→3p) differential and total electron excitation cross sections by using the Born approximation. As would be expected, significant differences in the results are found, and the calculation can be used as an example in elementary quantum mechanics to demonstrate just how much variation in the cross section and line strengths there is for Na(3s→3p).

ISSN:0002-9505    

DOI:10.1119/1.10158

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

The simple example of the gravitational instability of an infinite homogeneous medium first examined by Jeans is treated within the framework of Newtonian mechanics. The special case of a self‐gravitating, isothermal ideal gas is considered as an example to illustrate subtle errors in past work.

ISSN:0002-9505    

DOI:10.1119/1.10159

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

The motivation, derivation, and properties of some unitary transformations of the Dirac equation are discussed, including the Foldy–Wouthuysen, Cini–Touschek, and Melosh transformations as members of a general class of such transformations. In addition, some spin‐1 considerations are outlined, as well as a way of dealing with free massless electrons and Maxwell’s equations in a format parallel to rest‐system considerations.

ISSN:0002-9505    

DOI:10.1119/1.10160

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

The generalized Bernoulli construction is used to study the equation of state of rigid particles in two and three dimensions. A system of hard squares is considered in detail, and results for hard cubes, disks, and spheres are also presented. The discussion permits the introduction of the mean‐free‐path problem in the equation of state, and the result of the virial theorem of Clausius is obtained for these systems. This heuristic method can be used to discuss the equation of state at low and high densities without the use of formal theories.

ISSN:0002-9505    

DOI:10.1119/1.10534

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP