Describes three demonstrations/activities that involve forces: (1) a canoe-like boat made from copper window screen; (2) magnetic forces with a paper clip and ceramic magnetic; and (3) an "icemobile" machine that cuts ice cubes without an obvious source of energy. (DH)

Procedures for displaying computer-generated text and graphics to a large audience are inexpensive when a Fresnel-mirror projector is used. Although small liquid-crystal displays (LCDs) can be easily projected, large LCDs require some modification (which is described). Other devices with LCD displays (oscilloscopes, televisions, and pulse-height…

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)

Discusses: (1) feature of videodisc technology which make it a versatile educational tool; (2) availability of videodiscs for teaching physics and astronomy; and (3) example of the ways these videodiscs can be used in instructional settings. Tables listing physics and astronomy videodiscs (title, author, source, cost, and abstract) are included.…

Explains "maintenance free" car batteries which do not involve any changes in principles from traditional car batteries (which require the addition of distilled water). The newer systems have reduced water loss to near zero by improvements in the batteries themselves and in the electrical systems which charge them. (JN)

Scientists often use the "slingshot effect" (also called the "gravity assist") of the gravitational field of a planet to increase or decrease the velocity of a spacecraft. Examples of this effect, puzzling aspects, a qualitative explanation, details of necessary calculations, a thermodynamic analogy, and other topics are discussed. (JN)

Discusses a series of experiments performed by Thomas Hope in 1805 which show the temperature at which water has its maximum density. Early data cast into a modern form as well as guidelines and recent data collected from the author provide background for duplicating Hope's experiments in the classroom. (JN)

Working principles and operating characteristics of the extremely compact and highly efficient semiconductor lasers are explained. Topics include: the p-n junction; Fabry-Perot cavity; heterostructure semiconductor lasers; materials; emission characteristics; and single-frequency semiconductor lasers. Applications for semiconductor lasers include…

Describes a simple three-dimensional model of Halley's Comet orbit (which is much more informative than a two-dimensional drawing) to illustrate spatial relationships and visualize how the comet moves relative to the earth. Instructions for model assembly are given along with a template which can be photocopied and glued to cardboard. (JN)

Misconceptions occur because the caliper is often read with the same significant figures as a meter stick; however, the precision of the vernier caliper is greater than the precision of a meter stick. Clarification of scale reading, precision of both tools, and significant figures are discussed. (JN)

Presents two simple techniques for physics demonstrations: (1) a projection lens system for oscilloscopes which uses an inexpensive surplus lens and enables the entire class to observe the screen; and (2) a polarized optical "Cheshire cat" which uses the overhead projector and Polaroid sheets. (JN)

Explains two activities: (1) a "rotator demonstration" (a turntable, pendulum, chalk, and other materials), which can be used in many activities to demonstrate rotational concepts; and (2) an "Eskimo yo-yo," consisting of two balls (plus long strings and a glass tube) which rotate in opposite directions to show centripetal force. (JN)

Addresses the question of why a dog's eyes appear red and glow when a flash photograph is taken. Conditions for the red-eye effect, light paths involved, structure of the eye, and typical cameras and lenses are discussed. Also notes differences between the eyes of nocturnal animals and humans. (JN)

Explains the physical principles which result in various colors of the sky. Topics addressed include: blueness, mystical properties of water vapor, ozone, fluctuation theory of scattering, variation of purity and brightness, and red sunsets and sunrises. (DH)

Compares and contrasts high school physics philosophies, curricula, and textbooks of early 1900s to present, indicating that current textbooks are teacher and subject-oriented, lack examples of daily life, and are highly mathematical and too abstract. Suggestions for helping students experience success and improve self-esteem (which leads to…