摘要:

The preparation of bodies which have the property that the mass center lies on the periphery is here considered. It is demonstrated that, starting from a large variety of shapes, including all those here called “medially convex,” it is always possible to prepare a centroidally bordered shape by cutting a simple triangular notch out of the basic shape. Incidentally it is proved that every area which is medially convex with respect to a basebis at least8/3times as great as the area of the centroid triangle constructed on the baseb. The method of triangular notching is applied in detail to several familiar shapes, including the general trapezoid and circular segment. The preparation of a centroidally bordered shape from a basic shape which includes a straight angle in its boundary is also considered. The solution by quadrilateral notching is indicated but not carried through in detail. The simple solution for the special case of the balancingLis written down and illustrated photographically.

ISSN:0002-9505    

DOI:10.1119/1.1933927

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

If nuclear lengths, masses, times, energies, actions, etc., are compared with corresponding cosmological quantities, the resulting dimensionless ratios are near unity or near a small, half-integral power of1080, which is picturesquely called the “number of particles in the universe.” These “numerical coincidences” are collected and shown to imply probably a single relation between atomic and cosmic structural constants. They may be used to define two systems of units such that any quantity has a measure in the “elementary” system which is an integral power of1040times its measure in the “cosmical” system. Both systems are theoretically convenient, the “elementary” havingcandhunity, and the “cosmical” havingcandGunity.

ISSN:0002-9505    

DOI:10.1119/1.1933928

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

An undergraduate experiment is described for determining thermodynamic temperature directly from the definition of entropy. A simple system is arranged so that the entropy change due to the addition of heat may be calculated from the resulting change in the pressure exerted by the system. For this calculation the isentropic thermal expansion of the system must be determined experimentally. It is shown that in principle the temperature as determined does not require calibration of the thermometer used except at two fixed points. Accuracy of the order of 1 percent can be attained.

ISSN:0002-9505    

DOI:10.1119/1.1933929

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

A simple and challenging freshman laboratory experiment for the quantitative study of gyroscopic precession.

ISSN:0002-9505    

DOI:10.1119/1.1933930

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

Certification of physics teachers involves more than appropriate regulations. Members of college and university physics departments must participate in training good students for teaching positions in the schools. The development of appropriate state regulations and their intelligent interpretation into programs of study effective in producing physics teachers, who are to a degree scientists, involves effort on the part of physicists.This paper reports on work in physics teacher certification initiated and to a large extent carried out by K. Lark-Horovitz, Head of the Department of Physics at Purdue and first Chairman of the AAPT Committee on the Teaching of High School Physics.

ISSN:0002-9505    

DOI:10.1119/1.1933932

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

An interesting assembly of nineteenth-century scientists is here reproduced. It is likely, however, that it was not made from life, but was assembled from separate photographs.

ISSN:0002-9505    

DOI:10.1119/1.1933933

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

The sonometer to be described is unique because of its electromagnetic nature. Its application to the vibrating string experiment makes practicable an important experiment which has hitherto been difficult to perform. This sonometer makes it possible to demonstrate both sound and electrical experiments with very reliable results.

ISSN:0002-9505    

DOI:10.1119/1.1933934

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

A review and discussion of George Sarton's new booksAncient Science through the Golden Age of GreeceandA Guide to the History of Sciencewith added reflections on the teaching of the history of physics.

ISSN:0002-9505    

DOI:10.1119/1.1933935

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

A laboratory course especially organized for college seniors is described and remarks concerning its administration and improvement are set down along with some general ideas concerning the laboratory training of senior physics students.

ISSN:0002-9505    

DOI:10.1119/1.1933936

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

A simple and inexpensive vacuum tube circuit is presented which is suitable for demonstrating elementary oscillatory phenomena at a frequency of about14cycle per second. With this equipment, it is possible to follow visually, on a meter or recorder, the individual excursions of the system.

ISSN:0002-9505    

DOI:10.1119/1.1933937

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP