This paper presents a derivation of the number given by Fermi in 1925, in his semiclassical treatment of the motion of an electron in the field of two stationary positive charges, for Bohr quantization of the electron orbits when the stationary charges are positive, and applies it to an electron moving in the field of a stationary dipole.…

Describes a dynamical system which is stable at potential maxima. The maxima, called L-4 and L-5, are stable locations of the restricted three-body problem. Energy loss from the system will tend to drive it away from stability. (GA)

Describes an experiment which studies the motion of an irregular Lucite glider on an air table and demonstrates the dynamic properties of the center of mass. (Author/GA)

Derives the precessional period of a Foucault pendulum without using small oscillation amplitudes. Shows that if the path of the pendulum passes through the origin, the periods for differing amplitudes are essentially the same. (GA)

Analyzes the physical explanation accounting for tendency of Laboratory spring-mass oscillators to swing sideways. (SL)

The three possible fates of burned-out stars: white dwarfs, neutron stars and black holes, are described in elementary terms. Characteristics of these celestial bodies, as provided by Einstein's work, are described. (CP)

Demonstrates that if a sinusoidal oscillation of the point of support of a pendulum is approximated by a square wave, a matrix method may be used to discuss parametric resonance and the stability of the inverted pendulum. (Author/SL)

A physicist's view of the problems involved in kicking a football is described through the principles of projectile motion and aerodynamics. Sample equations, statistical summaries of kickoffs and punts, and calculation of launch parameters are presented along with discussion to clarify concepts of physics illustrated by kicking a football. (JN)

Examines, in three experiments, infant sensitivity at 20, 30, and 36 weeks of age to 3-dimensional structure of a human form specified through biomechanical motions. Findings are interpreted as suggesting that infants, by 36 weeks of age, are extracting fundamental properties necessary for interpreting a point-light display as a person. (Author/BE)

Presents algorithms for the simulation and motion display of the three basic kinematic devices: (1) four bar linkages; (2) the slider crank; and (3) the inverted slider crank mechanisms. The algorithms were implemented on a Commodore-VIC 20 microcomputer system with 6500 bytes of available memory. (Author/JN)

Presents information on the moment of inertia of a tennis racket about its principal axes. This information (not available from conventional sources) is useful since it influences how the racket plays and how the racket feels when it is swung. In addition, measurements of motion can be easily made by undergraduate students. (JN)

Explains a projectile motion experiment involving a bow and arrow. Procedures to measure "muzzle" velocity, bow elastic potential energy, range, flight time, wind resistance, and masses are considered. (DH)

Describes a computer program (for Apple II microcomputers) which simulates motion in a quadratic resisting medium. Descriptive equations, program inputs and outputs, and program evaluation are considered. Program listing and/or program on initialized disk may be obtained by contacting the author. (JN)

Many people erroneously believe that an object carried by another moving object will, if dropped, fall in a straight vertical line. This belief may stem from a perceptual illusion in which objects dropped from a moving carrier are perceived as falling straight down or even backward. (Author/RD)

Starting from a situated cognition perspective, this paper reports on the activity of 9th grade students who are interpreting the shape of a graph arising from the motion of a bouncing ball. In an unfamiliar context, informed by previous knowledge of similar experiments, the obstacle of understanding why the graph does not start from the origin is…