Today, almost all introductory physics textbooks include standardized "rules" on how to find the number of significant figures in a calculated value. And yet, 30 years ago these rules were almost nonexistent. Why have we increased the role of significant figures in introductory classes, and should we continue this trend? A look back at…

In the popular press, diagrams showing the evolution of the universe begin with a great jump in size labeled "inflation." Can we explain the basic ideas behind inflation to our students who have taken our introductory physics course? Probably not. In our standard introductory physics courses, even those with special relativity, something…

A television advertisement and a website present an interesting question: can rail company CSX "really" move a ton of freight 468 miles on a gallon of fuel, or is the claim preposterous? Let us examine the claim, first by understanding what is meant, looking at their data, and then converting units to examine the claim quantitatively.

We demonstrate that the time profile of the light intensity from domestic lighting sources exhibits simple yet interesting properties that foster lively student discussions. We monitor the light intensity of an industrial fluorescent lamp (also known as TL) and an incandescent bulb using a photodetector connected to an oscilloscope. The light…

The ordinary 12-oz beverage cans in the figures below are not held up with any props or glue. The bottom of such cans is stepped at its circumference for better stacking. When this kind of can is tilted, as shown in Fig. 1, the outside corners of the step touch the surface beneath, providing an effective contact about 1 cm wide. Because the…

For decades now, the laser has been used as a handy device for performing ray traces in geometrical optics demonstrations and laboratories. For many ray- trace applications, I have found the laser level 3 to be even more visually compelling and easy for student use than the laser pointer.

In this study, our basic contention was that it is essential for researchers to answer the question, "Where does cognitive conflict really arise from?" with more precision than has heretofore been attempted. First, we examined how the term "cognitive conflict" has been treated in the existing literature and try to pinpoint some difficulties,…

In the introductory physics courses at Wartburg College, we have been working to create a lab experience focused on the scientific process itself rather than verification of physical laws presented in the classroom or textbook. To this end, we have developed a number of open-ended modeling exercises suitable for a variety of learning environments,…

The sight of a broken bat in Major League Baseball can produce anything from a humorous dribbler in the infield to a frightening pointed projectile headed for the stands. Bats usually break at the weakest point, typically in the handle. Breaking happens because the wood gets bent beyond the breaking point due to the wave sent down the bat created…

During the AAPT summer meeting at Creighton University in 2011, Vacek Miglus and I took pictures of early apparatus at the Creighton physics department. The apparatus in the left-hand picture, shown with the spigot closed, appeared to be a liquid-level device: the water level was the same in both the narrow tube and the flaring glass vase.…

We discuss how light acquired a velocity through history, from the ancient Greeks to the early modern era. Combining abstract debates, models of light, practical needs, planned research and chance, this history illustrates several key points that should be brought out in science education.

Here is a way to show a sound wave travelling through air in real time. The method employs a set of low-cost microphone--LED units and demonstrates the movement of a pulse of sound as it lights up LEDs along a long (100-200 m) distance across a field. (Contains 4 figures.)

Assuming a constant mass decrease per unit surface and unit time we provide a very simplistic model for the dissolution process of spherical candies. The aim is to investigate the quantitative behaviour of the dissolution process throughout the act of eating the candy. In our model we do not take any microscopic mechanism of the dissolution…

This experimental activity aims to visualize the variations in the tension force on a rope with a mass attached to it in horizontal and vertical circular motion. The results facilitate comprehension of the effect of the direction of the radial force in changing the magnitude of the tension force. (Contains 10 figures.)

Calculation of moments of inertia is often challenging for introductory-level physics students due to the use of integration, especially in non-Cartesian coordinates. Methods that do not employ calculus have been described for finding the rotational inertia of thin rods and other simple bodies. In this paper we use the parallel axis theorem and…