摘要:

The view is first developed that it was in the effort of Copernicus' successors to justify fundamentally the validity of the change of conception usually associated with his name that the science of dynamics took a systematic shape. Then Newton's argument is examined that the ptolemaic alternative must mean a disruption of the solar system which is not witnessed and, therefore, the Copernicus-Kepler scheme ought to be accepted absolutely. This particular reasoning of Newton is shown, however, to suffer from a defect. The basis of others of Newton's arguments on the subject is considered, and it is presented that the application of dynamical principles makes the copernican standpoint on planetary motions no more final than the high degree of probability adduced in its favor by Copernicus himself on the ground of its merit of simplicity and harmony as compared with Ptolemy's picture.

ISSN:0002-9505    

DOI:10.1119/1.1932773

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:10.1119/1.1932774

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

The development of modern physics requires that verbal interpretations given to the symbols used in mathematical analysis be closely examined to determine whether such verbal interpretations are meaningful or even possible. The concept “causality” is studied. Considerations suggested by relativity theory indicate that this concept can have only a local meaning and that, in particular, two observers in different parts of the universe could not communicate adequately with each other if they employed the concept of causality in their statements of physical phenomena. It is requisite that the scientist give up his insistence on verbal translations of abstract symbols in order that he be able to make more general and profound insights in his analytical reasoning.

ISSN:0002-9505    

DOI:10.1119/1.1932775

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

An electronics laboratory course developed primarily for junior and senior students in physics is described. Emphasis is placed on the theory of operation of vacuum tubes and their uses as circuit elements in research applications. The equipment, largely home-constructed and described in some detail, is provided in a form which allows quick assembly by the student, and individual components are designed to provide maximum flexibility in setups.

ISSN:0002-9505    

DOI:10.1119/1.1932776

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

A sample outline of objectives illustrates a method of laboratory instruction in elementary electricity in terms of student behavior. The twenty-six specific objectives are grouped under five categories: instrumental skills, skills in the use of the controlled experiment, problem solving skills, miscellaneous skills, functional understanding of principles and habits.

ISSN:0002-9505    

DOI:10.1119/1.1932777

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

The discovery of neutrons produced by the cosmic radiation is reviewed, and the evidence today available is summarized. The life history of a neutron in the atmosphere is discussed, as is its eventual capture to form radiocarbon. The latitude effect and altitude dependence are presented. Some of the possible production-processes are discussed.

ISSN:0002-9505    

DOI:10.1119/1.1932778

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

The regularity of alpha-radioactivity is usually illustrated by the Geiger-Nuttall Law. Guided by the quantum-mechanical solution of the problem of alpha-particle emission, a way of plotting these data is shown, which yields a more satisfactory straight line than the Geiger-Nuttall plot.

ISSN:0002-9505    

DOI:10.1119/1.1932779

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

Several standard demonstration experiments in electromagnetic induction, as performed with newly designed or modified apparatus are described. One of these, Arago's disk, employs a rotating magnetic field so that torque measurements can be made on the (almost stationary) disk. A series of auxiliary measurements shows that the torqueTcan be represented in terms of the fluxφby the relationT = 1.55φ2, whenTis in g wt×cm, andφis in kilogauss.

ISSN:0002-9505    

DOI:10.1119/1.1932780

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

Brief derivations of dispersion and resolving power give their expression in terms of the directly measurable angle of the prism and its angle of deviation at different wavelengths. Elimination of the length of the prism base seems to improve student understanding of the quantities. Students' experimental results are given to show the precision to be expected.

ISSN:0002-9505    

DOI:10.1119/1.1932781

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP

摘要:

A brief exposition (descriptive rather than quantative) is given of some of the common phenomena of compressible flow. The aim of the paper is to supply background material to the physicist who may wish to know a little more about the problems and techniques involved in the mechanics of compressible fluids.A graphical representation of a point source moving through a fluid at various velocities from subsonic to supersonic is given and described. There is also a description with sketches of the principal optical methods of wind-tunnel testing for compressible flows. A number of actual test photographs is included which show the type of picture obtained by the various test methods and which also show the formation of shock and Mach waves.

ISSN:0002-9505    

DOI:10.1119/1.1932782

出版商:American Association of Physics Teachers    

年代:1951

数据来源: AIP