ISSN:0002-9505    

DOI:10.1119/1.15147

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15118

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15095

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15098

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15100

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

Problem solving in physics requires a certain quantity of knowledge of the subject matter: principles, procedures, etc. In addition, the problem solver must be able to access these principles and procedures in a given situation. Investigations have shown that failure in problem solving is often caused by lack of availability of knowledge, and also that availability is closely related to the organization of knowledge in memory. Opinions differ, however, on whether the optimal form of this organization should be centered around problem types or arranged in a hierarchical way. In this study two concrete examples of knowledge structures in the field of electricity and magnetism are compared. An experiment is also described, in which the actual knowledge structure of beginning students was studied. The outcome indicates that students with good results in problem solving organize their knowledge more in accordance with problem types than do students with poor results. The results of the experiment are discussed in the light of the two knowledge structures described. The possible role of these structures in physics teaching is treated in the final paragraph.

ISSN:0002-9505    

DOI:10.1119/1.15101

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The conceptual basis of assigning a beginning and an age to the universe is discussed, especially with regard to big bang scenarios.

ISSN:0002-9505    

DOI:10.1119/1.15102

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

A simple theory of magnetic braking in a thin metal strip is proposed. The predictions of the model are compared to experiment and good agreement is obtained. The experimental tests were conducted by spinning a thin aluminum disk of large radius between the pole pieces of an electromagnet. A field range of 0 to 150 mT was used.

ISSN:0002-9505    

DOI:10.1119/1.15103

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

Some common errors exhibited by students in interpreting graphs in physics are illustrated by examples from kinematics. These are taken from the results of a descriptive study extending over a period of several years and involving several hundred university students who were enrolled in a laboratory‐based preparatory physics course. Subsequent testing indicated that the graphing errors made by this group of students are not idiosyncratic, but are found in different populations and across different levels of sophistication. This paper examines two categories of difficulty identified in the investigation: difficulty in connecting graphs to physical concepts and difficulty in connecting graphs to the real world. Specific difficulties in each category are discussed in terms of student performance on written problems and laboratory experiments. A few of the instructional strategies that have been designed to address some of these difficulties are described.

ISSN:0002-9505    

DOI:10.1119/1.15104

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

We consider a simple Atwood machine consisting of a massless frictionless pulley no. 0 supporting two massesm1andm2connected by a massless flexible string. We show that the string that supports massless pulley no. 0 ‘‘thinks’’ it is simply supporting a massm0, withm0=4m1m2/(m1+m2). This result, together with Einstein’s equivalence principle, allows us to solve easily those compound Atwood machines created by replacing one or both ofm1andm2in machine no. 0 by an Atwood machine. We may then replacing the masses in these new machines by machines, etc. The complete solution can be written down immediately, without solving simultaneous equations. Finally we give the effective mass of an Atwood machine whose pulley has nonzero mass and moment of inertia.

ISSN:0002-9505    

DOI:10.1119/1.15105

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP