摘要:

An advantage of thegeneral principleapproach to physics as contrasted to the particularized formulation of physical relationships is exemplified by the solution of a research problem in ionospheric radio propagation. The generalized approach resulted in the construction of a mechanical analog computer which can be used to demonstrate Fermat's principle. This paper outlines briefly the theory ofleast action, shows how it can be applied to mechanical systems, electrical circuits, and ray optics to obtain the more familiar laws describing their behavior, and describes the essential similarity between an optical system and its mechanical analog. The mechanical demonstrator can be assembled from common laboratory equipment for classroom demonstration, or it can be carefully constructed for use in computing tables of radio propagation times for ray paths bounded by the earth and ionospheric layers.

ISSN:0002-9505    

DOI:10.1119/1.1932688

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

Four problems, a, b, c, and d, are proposed which deal with the application of (a) constant force to a massm, (b) constant torque to a body with rotational inertiaI, (c) constant emf to a condenser with capacitanceC, and (d) constant emf to a coil with inductanceL.In (a) and (b) the acceleration is prevented by having the massmin one case and momentIin the other increase at the proper rate. In (c) and (d) the current is kept constant by having the capacitance in one case and the inductance in the other increase at the proper rate. The power required is shown to be constant in each case and the distribution of energy supplied to each element turns out to be equally divided between kinetic energy, in (a) and (b), or field energy, in (c) and (d), and some system of restraints such as friction, springs, etc., which inevitably opposes the required change of the elements,m, I, C, andL.

ISSN:0002-9505    

DOI:10.1119/1.1932689

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

Remarks upon the present shortcomings of publications dealing with physics at both scholarly and popular levels of exposition, with suggestions for improvement.

ISSN:0002-9505    

DOI:10.1119/1.1932690

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

Large enrollments and relatively restricted teaching staffs have in recent years increased the challenge to teachers. But in addition to this, the diminished emphasis, that was generally adopted earlier in the century, on the recitation as a teaching method, has left limited opportunity, or none at all, for adequate oral self-expression in the classroom. Such training, it is felt, is indispensable to the student's broadest development, whatever other methods, however meritorious, may be used. The problem is serious and requires attention. It is discussed here in some detail.The question is raised whether now, in too many institutions, the lecture method is over-stressed, encouraging too much in students an habitual dependence on the lecturer, with a resulting lack of development of dependence upon themselves

ISSN:0002-9505    

DOI:10.1119/1.1932691

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

The experimental results forn-pandp-pscattering at high energies are described, and a review of the present status of theoretical interpretation is given. For the scattering of 90-Mev neutrons by protons the angular distribution indicates that only even states of angular momentum are strongly effective. Evidence of the operation of exchange forces is mentioned. In the scattering of 32-Mev protons by protons the angular distribution is appropriate tos-state interaction alone. The 340-Mevp-presults indicate the existence of noncentral (tensor) forces in states of odd orbital angular momentum.

ISSN:0002-9505    

DOI:10.1119/1.1932692

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

Data are presented showing the enrollments of undergraduate and graduate students in physics in approximately 500 colleges and universities in the United States. In the academic year 1949–50, 12,670 undergraduate and 5,560 graduate physics majors were enrolled. These numbers are about twice those of four years previous. During 1948–49 the number of degrees in physics granted were: bachelors, 3,495; masters, 920; doctors, 274. For 1949–50 the number of degrees to be granted was estimated as: bachelors, 4050; masters, 1,000; doctors, 340. The production of doctorates in physics has now reached a “normal” output, based on previous trends which indicated a rapid increase. A tabulation is presented of the bachelors, masters, and doctors degrees granted in 1948–49 by each of the 500 colleges and universities in the United States.

ISSN:0002-9505    

DOI:10.1119/1.1932693

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

The advantages in application of the generalized area-moment propositions developed by the author over the restricted forms of the same originally developed by Mohr are illustrated by detailed application to two standard cases in beam theory, in particular to the case of a simple beam with a concentrated load placed off center, and of an overhanging beam with a concentrated load placed at the free end.

ISSN:0002-9505    

DOI:10.1119/1.1932694

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

The paper presents a review of recent work onit-capture of orbital electrons by nuclei, including a simple outline of the underlying theory and a discussion of the conditions under which the phenomenon occurs. A brief description is given of the instruments and methods used to observeK-capture.

ISSN:0002-9505    

DOI:10.1119/1.1932695

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

A laboratory exercise in photographic emulsion track measurement is described, adaptable to any student level from the sophomore to the first-year graduate. The prime objective is student observation of emulsion tracks, and the unique pedagogical advantages of this recording medium are considered. Details of procedure and analysis of data are discussed.

ISSN:0002-9505    

DOI:10.1119/1.1932696

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

When an observer moves over the face of the earth, there is a change in both the magnitude and the direction of the apparent acceleration due to gravity. At speeds now becoming attainable, the change is just about observable with modern aircraft navigating instruments. The change consists of two terms—a Coriolis term and a centripetal term. If a particle could be dropped through a vacuum from an aircraft flying a great circle course, the Coriolis deflection of the falling particle,as seen by the airman, would be independent of the aircraft's velocity.

ISSN:0002-9505    

DOI:10.1119/1.1932697

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP