bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comments on Several Friction Phenomena
Authors: Brewington G. P. 
Published: August 2005

It is suggested that the term dry friction be limited to phenomena observed under highly outgassed conditions. Two theorems are suggested, one on the distribution of heat energy between two friction surfaces and the other on the independence of the heat loss in certain clutches, on the coefficient of friction.
Several suggestions using concepts of the physics of the solid state are made to give a better picture of the ultimate cause of friction.
Shapes of Craters Formed in Plaster of Paris by Ultra-Speed Pellets
Authors: Rinehart John S. , White W. C. 
Published: August 2005

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 weighed 23 g and 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 from 12 in. 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.
Geometrical and Graphical Representations of Lissajous Figures
Authors: Fahy Edward F. , Karioris Frank G. 
Published: August 2005

The fact that a sine curve, wrapped on the surface of a circular cylinder and projected orthogonally on a plane, will in certain cases produce Lissajous figures is used to develop a simple geometrical model which will demonstrate these curves. It is pointed out that natural generalizations of Lissajous figures can be obtained through this model.
The use of sine-sine graph paper for plotting and analyzing Lissajous figures is also described.
Velocity-Dependent Potentials for Particles Moving in Given Orbits
Authors: Coffman Moody L. 
Published: August 2005

Velocity-dependent potential functions can sometimes be used to determine the field of force that can be applied in order that particles may move in specified paths. In particular, the electromagnetic field vectors E and B can be determined from such a potential function if the paths on which charged particles move are specified.
The velocity-dependent potential U is related to the kinetic energy T and the Lagrangian function L by the equation U = T − L, where L is an arbitrary solution of the Lagrange equation (d/dt)(δL/δp′) − (δL/δp) = 0, where p = constant represents the orthogonal trajectories of the curves which describe the paths the particles are to follow. From the velocity-dependent potential function U, the field of force can be calculated by the definition Qp = −(δU/δp) + (d/dt)(δU/δp′).
Experimental Study of Sliding Friction
Authors: Maney Charles A. 
Published: August 2005

This article constitutes a report on an independent experimental study of the variation of the coefficient of sliding friction under very simple laboratory conditions. It is based on nonaccelerated motion involving sliding friction at speeds from 0.25 to 20 cm/sec. The experimental set-up consists of a weighted block resting upon a horizontal surface, subjected to the pull of various weights suspended over a pulley and attached to the block by means of a cord.
For all materials tested, including wood, leather, glass, and various metals, it is found that (1) the coefficient of sliding friction varies as the logarithm of the speed of the moving surface, increasing directly as the logarithm of the speed increases, (2) in the case of wood surfaces in contact, the coefficient of sliding friction decreases as the normal force increases, (3) in the case of both wood and leather surfaces in contact with other surfaces, the coefficient decreases with repeated performance, and (4) in the case of metal surfaces in contact, the coefficient of friction increases with repeated performance, unless the product of the abrasive action of friction is removed for each performance. The removal of the loose metallic particles causes a decreased coefficient of friction.
Possible Motions of a Sphere Suspended on a String (The Simple Pendulum)
Authors: Hughes J. V. 
Published: August 2005

The possible motions of a sphere suspended on a string are found to consist of combinations of (1) a pendulum type of motion and (2) a rolling motion, in which the ball rolls in angular harmonic motion about an axis very near its center. For (1) it is shown (a) the usual formula for the length of the equivalent simple pendulum should be replaced by L(1+2r2/5L2+4r3/25L3 +···), where r is the radius of the ball and L the distance of point of suspension to center of the sphere, and (b) the best way of starting this motion is to pull the ball aside by a horizontal force through its center. For (2) it is shown that the period of oscillation is very close to 2π(2r/5g).
Photographs are given showing experimental verifications of these effects.
A Graphical Demonstration of White Light Interference
Authors: Traub Alan C. 
Published: August 2005

A teaching device is described which can be used in lectures on the interference of white light. The wave forms of four selected components of white light, in the violet, green, yellow, and red regions, are shown one above the other on a cardboard chart, inked in their respective colors. A sheet of clear plastic with an identical set of waves drawn on it is placed over the chart so that the two sets are in register. The combination represents a beam of white light as it arrives at the retina. A retardation of part of the beam is illustrated by displacing the plastic sheet laterally. Since the sine waves differ among themselves in wavelength, the various phase changes which result among the four components are shown quite clearly.
The principle has been embodied in slide rule form with the wave trains appearing at a large plastic window. Five smaller windows indicate, respectively, path difference in millimicrons, dominant wavelength and purity of the resulting light when C.I.E. Illuminant C is used, and relative energies and resultant hue for the four components shown.
Demonstrations with Half-Wave Plates
Authors: Winans J. G. 
Published: August 2005

Cellophane of thickness to give 180° phase difference between O and E beams may be combined with polarizing sheets to make three types of windows. A design is cut in the Cellophane and it is mounted on the polarizer with effective optic axis 45° to the plane of vibration transmitted. The three types are (a) linear polarizer with half-wave Cellophane (b) linear/circular polarizer with half-wave Cellophane mounted on the side opposite the quarter-wave plate (c) linear/circular polarizer with half-wave Cellophane mounted on the same side as the quarter-wave plate.
Two windows of type (a) give eight different patterns depending on the arrangement. One window of type (a) permits detection of small degrees of polarization. With one window of type (b) and one of type (c) there are six possible patterns two of which do not change with rotation of one window with respect to the other. These effects result from the ability of a half-wave plate to rotate the plane of vibration through any angle or reverse the sense of circularly polarized light.
A Dynamic Model of Magnetic Resonance Phenomena
Authors: Verbrugge Frank 
Published: August 2005

A dynamic model to illustrate atomic and nuclear magnetic phenomena is described. An airdriven spinning magnetic dipole placed in a magnetic field exhibits a Larmor precession whose dependence on magnetic and gravitational parameters can be demonstrated. An ac magnetic field of variable frequency permits a visual demonstration of magnetic resonance.
Data obtained from the precession experiments can be used for a precise determination of the earth's magnetic field.
The Ionization Maintained in a Gas Before a Thin Plane Uniform Circular Source of Ionizing Particles
Authors: Fraser P. A. 
Published: August 2005

An expression is derived that gives a good representation of the volume rate of production of ion pairs in a gas before a thin plane circular uniform source of ionizing particles. The expression is valid when the radius of the source disk is restricted to be less than one-quarter of the range at maximum ionization of the particles. This is not a severe restriction for practical cases.
Curves and a table of this rate are given, in which distances are in units of the radius of the source disk, and hence are of general applicability within the restriction on the source disk radius.
This work has application to a number of fields, among them the study of the optical radiation from the region in front of such a source.
The Measurement of Laboratory Achievement. Part II. Paper-Pencil Laboratory Achievement Tests
Authors: Kruglak Haym 
Published: August 2005

This report deals with the analysis of paper-pencil laboratory tests in general physics, constructed and administered at the University of Minnesota, 1952–1953. The characteristics of the tests were investigated and the relationships with other achievement measures were explored.
With the exception of the Identification and Function, pretest intercorrelations were low. These two pretests were fair predictors for the corresponding posttests in Mechanics. All the pretests in Electricity were fair predictors for the corresponding posttests. The correlations between the paper-pencil tests and other criteria of achievement in elementary physics were either nonsignificantly different from zero, or low. On three of the four tests in Mechanics, boys scored significantly higher than girls. On all the posttests the means were significantly higher than for the pretests, irrespective of sex or course taken.
The investigation lends support to the hypothesis that paper-pencil laboratory tests contain elements other than those evaluated by performance tests and the conventional measures of achievement in elementary physics.
On the Functions and Mission of the American Association of Physics Teachers. Problems and Proposals
Authors: Schilling Harold K. 
Published: August 2005

This Association has to its credit many enviable achievements. It is suggested, however, that the present concepts as to its purpose and mission are inadequate for the future. Thus far in its history it seems to have been conceived of mainly an as association to hold meetings, to publish a journal, and to prepare, file, and occasionally publish committee reports. Having in mind the individual teacher, it has tried to give him encouragement, recognition, and inspiration, and opportunities to exchange ideas and experiences with his fellows.
The Association should become, to a much larger extent than in the past, an association for concerted and organized group study and action. Its goal should be to make of physics teaching a profession in the sense that law and medicine are professions. This will require more than that the Association give aid and encouragement to the individual teacher who endeavors to become more effective. It will require planned, systematic, and united attacks upon the problems of the profession as a whole and cooperative attempts to find solutions to such problems. It will require that the Association assert itself as the authoritative interpreter and official representative of physics teaching before the general public, other professional organizations, and government agencies; constitute itself a potent pressure group in behalf of our profession; help aggressively to maintain high professional standards; help improve conditions under which physics teachers must work; conduct cooperative educational experimentation and systematically attempt to improve physics teaching; collaborate with other agencies of higher education.
The past and current organization and modes of operation of the Association are not especially suitable for the realization of such purposes. Modifications and changes in these areas are suggested.
Three Interesting Instances of Rocking
Authors: Satterly John 
Published: August 2005

(1) Two equal thin circular rings are firmly jointed together at one point so that their planes are inclined to each other. The combination is placed on a rough horizontal plane and made to rock to-and-fro. The period is calculated and confirmed by experiment. Repetition is made with jointed disks.
(2a) A right solid cone is suspended by the vertex from a fixed point on a rough vertical plane. It is made to rock through small oscillations. The period is calculated and confirmed by experiment. (2b) A right solid cone results in equilibrium on a rough plane inclined to the horizontal. It is set rocking and the period calculated and confirmed by experiment. Repetition is performed with a thin conical shell.
(3) A thin circular ring is placed standing on a rough horizontal plane and leaning against a rough vertical wall. It is set rocking to-and-fro and the period calculated and confirmed by experiment. Repetition is made with leaning disks and wide bands. Variants of (3) are also performed.
Certification of Physics Teachers
Authors: Lefler R. W. 
Published: August 2005

Certification of physics teachers involves more than appropriate regulations. Members of college and university physics departments must participate in training good students for teaching positions in the schools. The development of appropriate state regulations and their intelligent interpretation into programs of study effective in producing physics teachers, who are to a degree scientists, involves effort on the part of physicists.
This paper reports on work in physics teacher certification initiated and to a large extent carried out by K. Lark-Horovitz, Head of the Department of Physics at Purdue and first Chairman of the AAPT Committee on the Teaching of High School Physics.
The Néel Theory of Ferrimagnetism
Authors: Smart J. Samuel 
Published: August 2005

The Néel theory of ferrimagnetism is a molecular-field theory of magnetic ordering in systems which contain nonequivalent substructures of magnetic ions. The two principal results of the theory are (a) the curve of reciprocal susceptibility vs temperature above the Curie temperature is an hyperbola, and (b) the curve of spontaneous magnetization vs temperature below the Curie temperature may have any one of a number of unusual forms. The exact form depends on the distribution of magnetic ions between the substructures and on the relative values of the molecular field coefficients.
The agreement between the predictions of the Néel theory and some experimental observations on ferrites is discussed briefly.
Critique of Teaching Objectives in Secondary Schools
Authors: Wise Harold E. 
Published: August 2005

Formal statements of the objectives of secondary education place major emphasis on the “common needs of youth” and minimize the importance of developing the potential abilities of outstanding students and their preparation for college. Emphasis in the preparation of teachers is on the professional aspects of teaching often at the expense of subject matter, while the school program suffers from a number of “maladies” such as “curriculum dilution,” the philosophy of “no failures,” and an excess of extra-curricular activities.
To increase the supply of potential physicists, it is suggested that emphasis be placed on the better preparation of teachers and on securing their continuing tenure on a 12-months basis at salaries comparable to those paid in professions requiring similar ability and preparation. To accomplish these ends, it is suggested that high school science and mathematics teaching be placed under Federal regulations somewhat similar to those which now govern Vocational Agriculture and Home Economics under the Smith-Hughes Law.
Effectiveness of the Case-General Electric Science Fellowship Program for High School Physics Teachers
Authors: Olsen Leonard O. , Waite Rollin W. 
Published: August 2005

The effectiveness of the Case-General Electric fellowship program for teachers of secondary school physics has been studied. The impact of the program on the training of scientific and engineering personnel through advanced training of physics teachers is discussed. An indication of the general problems faced by teachers in their respective schools is set down, along with specific examples of improved teaching.
The effect of the program is set forth convincingly through the results of a questionnaire sent to former Fellows.
The records of Fellow's students who attended Case have been examined. Their performance at Case is quite appreciably above the average, showing that more and better students are being trained for scientific and engineering careers as a result of the GE Science program.
A One-Semester Physics Course for Liberal Arts Students
Authors: Peck R. A. , Haisley W. E. 
Published: August 2005

The course described represents an attempt to lead freshmen not specializing in physics to an understanding of the nature of scientific endeavor which may provide an adequate scientific foundation for twentieth-century citizenship.
Holton's admirable general education text was employed to organize the study and define its semihumanistic approach. Equal attention was directed to a tightly integrated core of technical physics and to the interplay between science and the social environment. Technical material was organized about Newton's synthesis in mechanics and Bohr's in atomic structure. For the role of physics in human affairs subject matter was drawn from outside reading in selected historical and philosophical expositions and brought into the course through written papers and symposia. The customary laboratory curriculum was modified to provide a gradual increase in pace and difficulty throughout the semester.
Departures from conventional techniques are described in detail and their merits and shortcomings evaluated. Most of the innovations appear to have been successful in some degree.
Some Deterrents to Effective Teaching
Authors: Voeks Virginia W. 
Published: August 2005

At the University of Washington, students of 284 classes anonymously rated their teachers on clarity of lectures, awakening of interest, and three other matters. At the end of the rating scale were spaces for comments. Over 90% of the students wrote comments. For the 57 teachers whose mean rating on the scale was either in the top 10% or the bottom 10% of the faculty, we made statistical analyses of the comments by their 1503 students.
The two groups of teachers appear to differ fundamentally in their conception of the students and, consequently, in their techniques of motivation. The low-rated teachers seem to be seriously out-of-touch with their students and to view them cynically. For example, these teachers frequently dwell upon the obvious, repeat the text or their lectures too much, ridicule the students, ignore questions, and use much sarcasm. The top-rated teachers apparently rarely or never do these things.
Other statistically significant differences between the two groups also are presented and discussed.
Atomic Energy: An Adventure in Learning
Authors: Clancy Edward P. 
Published: August 2005

Some college students feel, by the time they reach their senior year, that they have in a sense been intellectually short-changed. Their views of important issues and ideas have been kept too narrow, and they have not been made aware of the relationships among the fields of knowledge.
An experimental program at Mount Holyoke College involving interdepartmental courses is discussed, and one of the courses—on atomic energy—is described. This course is taught by a staff which includes an economist, a political scientist, and a physicist. A sociologist gives considerable assistance.
Explicit Expression for Spherical Harmonics
Authors: Schmid L. A. 
Published: August 2005

A general expression for spherical harmonics as an explicit function of the angle coordinates is derived using standard methods of group-representation theory. This expression is more useful to physicists than a corresponding expression available in the mathematical literature for two reasons: (1) Its normalization is the one most commonly used by physicists, rather than one of several other normalization conventions used mainly by mathematicians. (2) Its form is especially convenient for use in the operator equations which occur in quantum mechanics. Furthermore, the derivation serves the pedagogical purpose of providing a simple illustration of the methods of group-representation theory.
A set of relations useful in solving the Dirac equation are listed, both because their verification provides an example of the utility of the expression derived, and because the form in which these relations are stated in the literature is apt to result in confusion stemming from the various different normalization conventions in use.
Résumé of Atomic Constants
Authors: Bearden J. A. , Thomsen John S. 
Published: August 2005

Some of the more interesting conclusions of a 1955 survey of atomic constants were the following. (1) Most familiar experiments described in general physics courses now carry negligible weight. (2) Probable errors in values of the constants are of the order of 10 ppm. (3) Use of x-ray “h/e experiments” has been a source of error in previous evaluations; theoretical interpretation of these results involves considerable uncertainty. (4) Electrochemical values of the Faraday are now in fair agreement, but their mean differs significantly from the value obtained by electromagnetic experiments. (5) There is still some evidence for variation of the velocity of light with frequency; however, the negative case appears stronger and is further strengthened by newer data.
Recent developments are discussed and the authors' analysis compared with the 1955 study of Cohen, DuMond, Layton, and Rollett. Recommended values for principal constants are given. These include a correction for an error in the Karplus and Kroll calculation of the anomalous moment of the electron, but do not reflect any experimental data reported since 1955.
Baccalaureate Origins of Ph.D. Physicists
Authors: Siebring B. Richard , Schwahn Duane H. 
Published: August 2005

Using the data gathered by the National Academy of Sciences about the baccalaureate origin of Ph.D. physicists for the periods 1936–1945, 1946–1950, and 1951–1955, the authors detected certain trends in the undergraduate training of Ph.D. physicists. It was found that the undergraduate training of physicists who earned doctorates during the years covered by this study was concentrated in a small proportion of this country's institutions of higher education. This concentration in the top institutions was found to be increasing.
The North Central states lost the lead in the undergraduate training of Ph.D. physicists to the Northeastern states. This is true both numerically and percentagewise. In terms of percentage contribution, the trend is toward the increasing influence of the technical schools (up 4.75%) rather than the colleges (down 5.2%) and universities (up 0.8%). The Ph.D. granting institutions have led the nongranting Ph.D. institutions over this time span and are increasing their percentage contribution. There is a slow trend from the privately controlled to publicly controlled institutions.