ISSN:0002-9505    

DOI:10.1119/1.12652

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.12642

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

The problem of ellipticity in the motion of the ordinary Foucault pendulum and the error caused by it are discussed. A simple method of slightly modifying the force–displacement relation in such a way that precession does not result from ellipticity is presented. The practical range of length of the Foucault pendulum is extended downward substantially. As experimental verification, results from a 70‐cm pendulum, mounted as a ’’wall clock’’ are given. Rates of turning from daily readings show a 2% rms deviation from the mean, and the long‐term average is within 2% of the rate calculated for the local latitude.

ISSN:0002-9505    

DOI:10.1119/1.12655

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Human history can be divided into three distinct successive phases. The first, comprising all history prior to about 1800, was characterized by a small human population, a low level of energy consumption per capita, and very slow rates of change. The second, based upon the exploitation of the fossil fuels and the industrial metals, has been a period of continuous and spectacular exponential growth. However, because of the finite resources of the Earth’s fossil fuels and metallic ores, the second phase can only be transitory. Most of the ores of the industrial metals will have been mined within the next century. The third phase, therefore, must again become one of the slow rates of growth, but initially at least with a large population and a high rate of energy consumption. Perhaps the foremost problem facing mankind at present is that of how to make the transition from the present exponential‐growth phase to the near steady state of the future by as noncatastrophic a progression as possible.

ISSN:0002-9505    

DOI:10.1119/1.12656

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Designating a +1200rotation (’’twist’’) of a corner cell of Rubik’s cubeTM(a popular geometric puzzle) as a (mathematical)quark, and a −1200rotation of a corner cell as a (mathematical)antiquark, the same restrictions that confine physical quarks are observed to hold, viz. isolated quarks cannot arise, and in general, combinations of quarks and antiquarks can only occur if the excess of one type over the other is a multiple of three.

ISSN:0002-9505    

DOI:10.1119/1.12577

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

There is increasing student and administrative demand for courses in the natural sciences that are accessible to undergraduates who are not majoring in a science. As the current trend to reimpose academic distribution requirements continues, the demand will increase still further. This paper describes a course that legitimately serves such a demand, and provides the nonscience student with an understanding of the methods and nature of natural science. The course is a seminar organized around a detailed examination of the Copernican revolution, in part through Copernicus’s original writings and in part through contemporary historical and philosophical analyses. The authors conclude that the course provides a successful model for achieving the aim of deepening the nonscientist’s understanding of what science is and how it proceeds.

ISSN:0002-9505    

DOI:10.1119/1.12578

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

We describe an electronic analog of a resistively shunted Josephson junction in which the quantum phase difference of a real junction is represented by the phase difference between two oscillators, each running at approximately 100 kHz. Only three integrated circuits and an external reference oscillator are required. The circuit operates on a time scale approximately 109times slower than a typical real junction and allows easy visualization of the time‐dependent quantum phenomena of the ac Josephson effect. Characteristic current–voltage curves and waveforms obtained with the analog are shown for the cases of dc and dc plus ac current bias, and for the sudden reduction of the critical current in a current‐fed, resistively loaded junction, which models a magnetically switched Josephson computer element. Other applications of the analog are discussed.

ISSN:0002-9505    

DOI:10.1119/1.12579

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

A simple model for inelastic scattering may be obtained by suitably generalizing scattering from a square well. The generalization introduces matrices into the quantum‐mechanical scattering equations. These equations may be solved exactly to give an explicit expression for the scattering matrix. In this paper we first describe and solve the model, and then discuss the results it predicts for a simple example. We will see that even a simple inelastic system can exhibit rich scattering behavior.

ISSN:0002-9505    

DOI:10.1119/1.12580

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

A class of rank‐ntensor theories of gravitation is considered. There is more than one theory for eachn≳0. All theories are Lorentz invariant and reduce to Newton’s theory for small velocities and weak gravitational fields. Among these theories is the second‐rank tensor theory of Whitehead and the spin‐two theory of Fierz and Pauli. The precession of the perihelion of a planet’s orbit is calculated for those theories withn= 0, 1, 2 and compared with the prediction of general relativity.

ISSN:0002-9505    

DOI:10.1119/1.12581

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

This the second of a three‐part series. This essay surveys evaluations of Dirac’s theory by other physicists, especially by Bohr who used Dirac’s speculations about negative energy electrons as evidence for the failure of quantum mechanics at nuclear dimensions.

ISSN:0002-9505    

DOI:10.1119/1.12643

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP