Approximately 50,000 people ran and walked down the street past my home in the 33rd annual running of the 10-km Bolder Boulder footrace on the morning of Memorial Day, May 30, 2011. In addition to the serious runners, there were many individuals dressed in all manner of amusing festival costumes; some were jogging and some were walking. Early in…

Two recent articles make prominent use of the concept of "apparent weight." The concept of "apparent weight" leads to two confusing inconsistencies. We need to know that with very little change in our representations, we can give our students an improved understanding of "weight" without ever having to invent the appealing but confusing concept of…

The following is a petition written over 36 years ago by University of Colorado students to the seven members of Colorado's delegation to the United States Congress. I was advisor to the student groups and found this when cleaning up my university office. It strikes me as being amazingly farsighted.

The article "Torsional Oscillations with Lorentz Force" by Paul Gluck provides a glimpse into the major world of ancient physics demonstrations in the late 19th and first half of the 20th centuries. The apparatus that was described and similar pieces of apparatus are the basis for many memorable but long forgotten educational demonstrations. The…

Defines frame of reference for the analysis of motion in a moving car, discussing the interaction of the car body, the seat springs, and the passenger when the car goes over a bump. Provides a related, but more advanced, problem with the motion of cars involving angular acceleration. (JM)

Describes the serendipitous discovery of paths left by charged particles in the magnetic deflection unit outside of a cyclotron. Offers suggestions for their occurrence. (CP)

Comments on a news item on rail traffic that is meant to promote conservation of energy. (GA)

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)

Four questions related to rain concerning aerodynamic drag force, pressure from the impact of raindrops, impact of wind on the pressure, and stopping force extended on the car by the water are proposed. (YP)

Reviews the concepts behind atmospheric optical phenomena such as rainbows and anticrepuscular rays. Describes the experience of observing these two phenomena simultaneously and calculates the probability of that observation. (JRH)

Described is an activity in which students examine data collected from an official report of a train accident to evaluate the conclusions of the official investigation. Quotations from the records and calculations used in this activity are included. (CW)

Attempts to determine, using estimations and current power-law relationships, whether a newspaper report concerning the statement that a single 40,000-kg truck does as much damage to the highway as 9,600 cars is true. Provides a mathematical and graphical possible solution. (MVL)

Discusses issues related to perpetual population growth. Argues that if we believe that there are no limits to growth, we will have to abandon the concept of a spherical Earth which puts limits to growth. (JRH)