We study the variation of the apparent weight of an object with height above the surface of a planet with a (buoyant) atmosphere. Interestingly, this variation depends on two competing factors--the reduced gravitational acceleration (which acts to reduce the weight with increasing height) and the reduced buoyancy force in the progressively less…

The Young-Laplace (Y-L) equation relates the pressure difference across the interface of two fluids (such as air and water) to the curvature of the interface. The pressure rises on crossing a convex interface such as a rain drop and falls on crossing a concave interface such as the meniscus of water in a glass capillary. The relation between…

Interactive classroom demonstrations (ICDs) are used extensively in physics, and prior studies indicate that, when conducted under certain conditions, they lead to appreciable increases in student gains and retention. The literature suggests that the ICD recipe for maximizing student gain is to (i) introduce the physical theory that will be…

There are many examples of using smartphones in physics experiments. Students and teachers can easily perform many physics experiments with the help of smartphone sensors, even experiments for which high-cost materials are needed. There are different types of such experiments in which various kinds of sensors are used. Many physical quantities can…

The "Next Generation Science Standards" (NGSS) encourages educators to help kindergarteners formalize a big idea in physics: A push or pull can cause an object to begin moving, speed up, slow down, stop, or change the direction it is going (NGSS Lead States 2013). In this article, the authors share an exciting, classroom-tested…

Peers play an important role in an individual's learning via collaboration. This study examined three semesters worth of student data collected through collaborative exams in a calculus-based introductory physics course. Participants were asked 142 physics problems over two rounds, and they answered the problems first individually (first round)…

Diffraction refers to a kind of optical phenomena which occurs when light approaches an element (object or aperture) whose features are in the range of the illuminating wavelength (small apertures, sharp edges). It can be explained by means of the undulatory nature of light or also geometrically by using simple ray optics. Diffraction phenomena…

In this paper, a simple method is described for visually demonstrating that the wavelength of light reduces when entering a medium of higher refractive index. When a violet laser (405 nm) is reflected off the surface of a Blu-ray disc (track spacing 320 nm) diffraction cannot occur since the wavelength is greater than the track spacing. However,…

This dissertation provides a start-to-finish description of development, administration, and validation for an online middle-school physics test using a DCM framework with response-time. The first paper illustrated the process of implementing DCM with a careful selection of the content domain and a simulation approach for a Q-matrix construction.…

Although the phrase "seat of EMF" in describing chemical cells has fallen into disuse, by distinguishing the distinct but incorrect conceptions both of Galvani and of Volta, in favor of the correct view of Faraday, "seat of EMF" it becomes possible (among other things) to understand: (1) why internal resistance really is…

We outline the physics involved in the use of scanning electron microscopy (SEM) and modernise the usual textbook treatment by explaining how one can now obtain high-quality images with non-conductive specimens. As a concrete example of an application in biology, we provide several magnification series of a flea obtained using SEM.

Among the student ideas about forces discussed in the literature, perhaps the most commonly reported is the notion of an impetus force, or the "belief that there is a force inside a moving object that keeps it going and causes it to have some speed." For example, Clement asked university students taking introductory mechanics to draw a…

In this paper we explain how to build a very sensitive force table using 3D-printed parts. The key component of this apparatus is a simple sensitive pulley that, together with the other components, can be printed in one day (one hour per pulley, 17 hours for a complete three-pulleys table) at the cost of 160 g of plastic filament. This force table…

Although the old problem of rotating liquid is described and solved in many textbooks and articles, the story still remains interesting. Intuitive understanding of the equipotential spatial surfaces is very difficult. This article is an attempt to present Newton's rotating tank in the light of the law of conservation of energy.

In 1981 I published a note on "Balancers" as part of a series of illustrations drawn from 19th-century physics texts. Some months later a wonderful present arrived from a physics teacher in Japan, showing the range of our journal. This was the Horse and Rider Balancer in Fig. 1 that was just like the woodcut in my note. The little…