摘要:

A necessary condition for effectively teaching physics is that the students have the capability of operating at the cognitive level that is matched with the logical structure that produced the discipline. Recent research indicates that a majority of students are not demonstrating this capacity. The analysis of the performance of students ’’learning’’ physics without the necessary cognitive development demonstrates behavior that hinders their intellectual growth.

ISSN:0002-9505    

DOI:10.1119/1.10144

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

Science and society questions on transportation are posed on such topics as energy intensiveness and efficiency, San Diego freeway noise, air pollution in the Los Angeles air basin, the 55‐mph speed limit, the ’’umbrella principle,’’ the Bay Area Rapid Transit (BART) system of San Francisco, and the hydrogen‐fueled airplane. Back‐of‐the‐envelope sophomore physics is utilized in attempting to answer the questions.

ISSN:0002-9505    

DOI:10.1119/1.10145

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

A simplification of the problem concerning the visual appearance of a rapidly moving sphere is presented. The approach brings out the uncontracted appearance of the sphere and its apparent rotation through the angle ϑ=sin−1(v/c) when viewed at an angle perpendicular to its motion. The problem is shown to be sufficiently simple to be a homework assignment in an undergraduate relativity course.

ISSN:0002-9505    

DOI:10.1119/1.10146

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

Formulas are derived for the energy, momentum, and angular momentum transmitted by waves of arbitrary shape in an inextensible string and by pure transverse waves in a suitably extensible string. The analysis is based on Tait’s procedure of viewing the wave from a moving frame of reference, and its application to the inextensible string, at least, is simple enough for use in elementary physics courses. The same method is used to find the elastic condition on an extensible string necessary for the propagation of mutually coherent shape and density waves. It is shown that the perfect transverse string waves referred to in textbooks can only be propagated in strings of the ideal Slinky spring type, and that they are incapable of carrying net momentum.

ISSN:0002-9505    

DOI:10.1119/1.10147

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

The interaction between charged particles and circularly polarized electromagnetic waves propagating parallel to a static magnetic field is an important problem in classical plasma physics owing to possible energy exchange at the cyclotron resonance. The nonlinear motion of ions in such fields is known to be described by elliptic functions, but the physics is obscured by the complicated expressions. The properties of the particle trajectories are much more transparent in the perturbation–expansion solution derived here. For small wave amplitudes the solutions are valid for an extended time and the resonance effects are clearly evident. The initial phase between the particles and wave fields emerges as an important condition on the motion. Potential applications of the results in magnetospheric physics and plasma fusion devices are briefly discussed.

ISSN:0002-9505    

DOI:10.1119/1.10540

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10541

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10542

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10543

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10544

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10545

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP