摘要:

The construction and use of an inexpensive rotating‐room apparatus is described. The device has a 48‐in.‐diam platform, seats four at a table, and rotates at four possible speeds. The two lowest, 0.4 and 0.6 rad/sec, are the most useful. It is easily transported and erected without special arrangements.

ISSN:0002-9505    

DOI:10.1119/1.9767

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

A study of human blood serum is utilized to demonstrate both the x‐ray emission caused by electrons dropping into atomic inner‐shell vacancies produced by proton bombardment and the application of such x‐ray emissions to trace element analysis. Sample preparation consisted solely of pipetting 25 μl of serum onto low‐ash filter paper. Characteristic Kαx rays from copper and zinc were detected by a Si(Li) semiconductor detector to determine trace concentrations of these essential biological metals in the blood. The copper and zinc concentrations in the blood serum sample analyzed were found to be 1.16±0.13 and 0.70±0.07 ng/μl, respectively.

ISSN:0002-9505    

DOI:10.1119/1.9768

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

In this simple experiment for an undergraduate laboratory a laser beam is passed through the mixing zone of two liquids with different refractive indices. The spatial variation of the refractive index, at different times during the mixing, can be determined from the observed deflection of the beam.

ISSN:0002-9505    

DOI:10.1119/1.9769

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

Kepler’s three laws of planetary motion are derived algebraically from conservation principles without introducing Newton’s law of force explicitly. This procedure can be presented to students who have had no more than high school algebra.

ISSN:0002-9505    

DOI:10.1119/1.9770

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

We develop a theory of orbits for the inverse‐square central force law that differs considerably from the usual deductive approach. In particular, we make no explicit use of calculus. By beginning with qualitative aspects of solutions, we are led to a number of geometrically realizable physical invariants of the orbits. Consequently, most of our theorems rely only on simple geometrical relationships. Despite its simplicity, our planetary geometry is powerful enough to treat a wide range of perturbations with relative ease. Furthermore, without introducing any more machinery, we obtain full quantitative results. The paper concludes with suggestions for further research into the geometry of planetary orbits.

ISSN:0002-9505    

DOI:10.1119/1.9771

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

Two calculations are presented of the probability of detection of an interstellar comet, under the hypothesis that such comets would escape from comet clouds similar to that believed to surround the sun. The results are that an encounter might have happened within historical times, although the simple assumptions used render the calculation uncertain to about a factor of 10. Three problems are proposed, each of which would be a reasonable term project for a motivated undergraduate and the answers to which would be of interest and are not presently known.

ISSN:0002-9505    

DOI:10.1119/1.9772

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

A theory of gravitation is developed which is a natural extension of the Newtonian theory. It is compatible with special relativity and with all present‐day observations. It requires only elementary mathematics and can be taught in a junior‐level mechanics course. It is not a complete theory of gravitation, since it applies only to static or quasistatic gravitational fields, but it enables the unmathematical to gain a good understanding of the physics of gravitation.

ISSN:0002-9505    

DOI:10.1119/1.9773

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

A heuristic derivation of aging in a gravitational field is given. Simple properties of Keplerian motion are used to obtain explicit expressions for the time lapse difference of two identical clocks in free fall which part and then meet again.

ISSN:0002-9505    

DOI:10.1119/1.10093

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

A lecture demonstration–thought experiment is described that has been effective in teaching the concept of the lack of simultaneity in introductory physics courses. The demonstration experiment can be used for studying the relationship between simultaneity and causality and as a conceptual device for analyzing the lack of simultaneity in special relativity thought experiments.

ISSN:0002-9505    

DOI:10.1119/1.10094

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP

摘要:

An account is given of some research projects undertaken by inner city high school students in the Physics Department at Drexel University during the last four years. The students, from low income families, are sponsored by the Neighborhood Youth Corps (which was established by the Economic Opportunity Act of 1964) with the hope that they will gain worthwhile work experience. Individual projects have included measurement of noise levels around the University, frequency analysis of impulsive sounds, effect of water content on Young’s modulus of various woods, effect of sulfuric acid exposure on the mechanical properties of wood, and the effect of air pollution, in the form of SO2, on the mechanical properties of wet wood. This latter project is being pursued vigorously; new and interesting results appear to be emanating from these particular studies. The article ends with the author’s feelings and conclusions about such a program, gained from four years of experience.

ISSN:0002-9505    

DOI:10.1119/1.10095

出版商:American Association of Physics Teachers    

年代:1975

数据来源: AIP