Researchers and practitioners alike express concerns about the conceptual difficulties associated with the concepts of momentum and kinetic energy currently taught in school physics. This article presents an in-depth analysis of the treatment given to them in 44 published textbooks written for UK secondary school certificate courses. This is set…

Notes that the rigorous kinetic theory, based on the Boltzmann equation, does not yield exact results although some texts claim this to be so. Stresses that they should be presented as approximations with an indication that refinements in the values are possible. (MVL)

Reports an experimental procedure for studying Einstein's theory of Brownian movement using commercially available latex microspheres and a video camera. Describes how students can monitor sphere motions and determine Avogadro's number. Uses a black and white video camera, microscope, and TV. (ML)

Discussed is the idea that models should be taught by emphasizing limitations rather than focusing on their generality. Two examples of gas behavior models are included--the kinetic and static models. (KR)

Provides an analysis of the forces causing the erratic motion of a knuckleball. Reveals the manner the ball should be thrown to provide maximum deflection. (Author/CP)

Presents an activity that enables students to answer for themselves the question of how fast a body must travel before the nonrelativistic expression must be replaced with the correct relativistic expression by deciding on the accuracy required in describing the kinetic energy of a body. (ZWH)

Discusses the physics of the "Ollie," a skateboard jump in which the skateboarder does not hold on to the board. The motion is described through three graphs that illustrate the positions of the tail of the skateboard, the center of mass, and the nose of the skateboard during a jump. (MDH)

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)

Newton's laws can be illustrated by having physics students participate in various activities while on roller skates. Several examples of such activities (including photographs) are provided. (JN)

Describes an apparatus which allows one to study the speed distribution, the gravitational distribution, and the mean free path of steel balls agitated into two-dimensional motion through collisions with the moving walls of their enclosure. (Author/GA)

Analyzes projectile motion using symmetry and simple geometry. Deduces the direction of velocity at any point, range, time of flight, maximum height, safety parabola, and maximum range for a projectile launched upon a plane inclined at any angle with respect to the horizontal. (Author/GA)

Describes the graphing calculator as a new graphical approach to standard physics problems. Presents a collision problem to illustrate its use. (JRH)

Explores the power transfer using (1) a simple electric circuit consisting of a power source with internal resistance; (2) two different mechanical systems (gravity driven and constant force driven); (3) ecological examples; and (4) a linear motor. (YP)

Outlines a simple method which shows the relation between work done in accelerating a mass and the resulting velocity of the mass. Equipment used includes a rubber ball, ramp of lumber, graph-chart, stopwatch, and hand calculator. (DH)

Describes a pendulum in which the spherical bob can roll on a track of the same arc as it swings when suspended by a cord. Comparison of the motion in the two mentioned cases shows the effect of rotational kinetic energy when the bob rolls. (GA)