摘要:

The equations of physics are often interpreted as purely numerical relations. Endowing the symbols with “dimensional” quality as well as magnitude leads to a simpler, yet rigorous, mathematical structure, and permits changing units by direct substitution. Analysis of the mathematical universe of discourse of physical equations shows also that the four-dimensionall,m,t,qsystem of units is actually simpler than a three-dimensional system.

ISSN:0002-9505    

DOI:10.1119/1.1927482

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

A series of measurements of theπ- and μ-mesonmasses and their decay energies is reviewed. Recent mass measurements made at the University of California Radiation Laboratory have employed an improved method in which the ratio of theπ-mesonmass to that of the proton and the ratio of theμ-mesonmass to that of theπ-mesonwere determined by measuring the ratios of ranges and ratios of momenta for particles of equal velocities. The absolute decay momentum of theμ-mesonwas also determined in the same series of experiments. Other experiments at the Radiation Laboratory in which quite different methods were used to obtain theπ-mesonmass and the decay energy of theμ-mesonare also discussed. The measurements are consistent with aπ-mesonmass of 276 electron masses and aμ-mesonmass of 210 electron masses. In addition, no contradiction is found for the assumptions that theπ − μdecay is accompanied by a neutrino and theμ − edecay is accompanied by two neutrinos.

ISSN:0002-9505    

DOI:10.1119/1.1933092

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1933093

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

Observations have been made on the craters produced in plaster of Paris targets by steel pellets that weighed 2 g and impacted at a velocity of 2.5 km/sec and by aluminum pellets that weighed23 gand impacted at a velocity of 4.7 km/sec. The angle of impact was varied from normal incidence to 75°. For angles of incidence between 0° and 45°, the mouth of the crater was substantially circular. At 60°, it had roughly the shape of an arrowhead. At 75° obliquity, the pellet ricocheted and produced an elliptical crater.The area of the mouth of the crater in every case was many times the area of the impacting particle. The craters were characterized by a large bowl-shaped excavation from12in. to 1 in. in depth with a shaft that extended a few inches into the plaster and whose area was approximately that of the pellet.The volumes of the holes have been measured and related to the impacting energy and momenta of the respective pellets.

ISSN:0002-9505    

DOI:10.1119/1.1933094

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

A report on the Radiological Monitoring Course offered as part of the Milwaukee Civilian Defense Program. In the first course 250 firemen, policemen, and people with technical background were trained in the principles of nuclear physics, and the effects, detection, and measurements of radiation. The course consisted of a series of lectures, together with appropriate films on the fundamentals of atomic and nuclear physics. The laboratory sessions consisted in familiarizing the trainees in the handling, reading, and care of three different radiation measuring instruments. Small radium sources were used. The field sessions consisted of the survey of a three curie cobalt-60 source at a local football stadium.

ISSN:0002-9505    

DOI:10.1119/1.1933095

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

Two rolling masses and three helical springs are arranged collinearly in a horizontal plane. Longitudinal vibrations of the system are excited manually and the two normal modes studied. Calculated and observed frequencies can be compared in detail, since the coupling constant is directly measured. Agreement is obtained to within a few percent.

ISSN:0002-9505    

DOI:10.1119/1.1933096

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

A method for the quantitative evaluation of chemicals as rocket propellants is described. The procedure utilizes the fact that adiabatic expansion through a nozzle may be considered to be isentropic. Treatments are presented for the two limiting conditions of expansion, corresponding to flow without chemical change and to flow which is characterized, at all times, by the existence of thermodynamic equilibrium.

ISSN:0002-9505    

DOI:10.1119/1.1933097

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

A description of the construction and operation of a replica of a coil, such as Nikola Tesla first described in 1891, is presented.

ISSN:0002-9505    

DOI:10.1119/1.1933098

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

An experiment applicable to an intermediate laboratory course in modern physics is presented. The method is fundamentally that used in 1910 by Rutherford and Geiger, with a G-M scaler and tape recorder replacing the scintillation technique. The experiment establishes the random nature of radioactive decay and introduces the student to the concept of statistical fluctuation.

ISSN:0002-9505    

DOI:10.1119/1.1933099

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

The concepts of space which are used in contemporary physics are discussed, and are contrasted with the older concepts associated with Newtonian physics. The effects of uniform motion on space and the simplest currently accepted relations between space and time are stated. Deviations from three-dimensional orthogonal space as demanded by the general theory of relativity are discussed, with attention to the relative roles of space and time terms in the space-time curvature associated with gravitational fields. The development of cosmo-logical theory, on the basis of general relativity concepts, is briefly indicated. Mach's suggestion for the relation of matter and space is described; more recent speculations relating over-all space and local properties, and the possibility of discontinuity in microscopic space, are noted. The emphasis in the current conception of space on interdependence between space and matter is pointed out.

ISSN:0002-9505    

DOI:10.1119/1.1933100

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP