Photogates play an important part of many of today's physics laboratory experiments. They signal when an infrared (IR) beam is interrupted, thus supplying the experimenter with important timing information. Currently photogates use an infrared photodiode (IR transmitter) and a phototransistor (IR receiver). User-built photogates have a weakness…

Einstein's special theory of relativity includes many non-intuitive and apparently paradoxical conclusions about space and time. One of these is time dilation, the fact that a clock moving relative to an observer runs slower than an identical clock at rest in the observer's reference frame. This is clearly exhibited in the extended mean lifetime…

The Leaning Tower is a long-time staple of the demonstration room. It can be traced as far back as apparatus catalogues from the 1850s. Some years ago, while teaching himself how to use a new wood lathe, Thomas B. Greenslade, Jr. made a replica of the original design. With the top removed, the tower is stable, but once the top is added, the line…

When authoring physics problems, professors may develop an intuition for how much information they need to provide such that the problem has a unique answer and is not over constrained. It is an open question as to whether using intuition leads to a sufficiently broad range of problems. In this paper we discuss a systematic way of authoring…

One of the memories of my freshman year at Amherst was a lecture in the required physics/calculus course in which Arnold Arons quoted Isaac Newton on standing on the shoulders of giants. Now that I have spent my physics career, I still use the same quote, but now apply it to the eponymous apparatus that has been designed by the giants in our field.

In high school and elementary college physics labs the measurement of vertical distance is often required. Measuring the distance an object falls or the vertical displacement of springs in a Hooke's law experiment are commonplace. Determining these distances to perhaps a millimeter or two of precision is difficult without an expensive height gauge…

The dynamics of a spring pendulum is an important topic in introductory experimental physics courses at universities and advanced science courses in secondary school education. Different types of pendulum setups with smartphones were proposed to investigate, e.g., the gravitational acceleration, to measure spring constants, or to illustrate and…

Recently, small computer fans have been demonstrated to be an effective method for teaching simple resistive circuits both qualitatively and quantitatively. The current through the fans is related to the rotational speed of the fans and allows multiple senses to be engaged (touch, sight, and hearing). Methods for learning simple circuits in an…

Here is presented an interesting problem that can be used to introduce students to a variety of physics topics including non-inertial frames and frictional forces, rotational dynamics, and damped oscillations; the normal force also appears, but not in its usual guises. The problem is a generalized version of problem 3.34 presented in the…

While physics is often promoted as being for everyone, its cultural narrative, i.e., what physicists do and who they are, has been and continues to be created by a dominant social group. As such, many students who come from marginalized backgrounds in physics are required to fit themselves into its narrow culture that does not reflect who they are…

The Arduino microcontroller is finding its way into labs throughout undergraduate physics curricula, from introductory courses to a variety of beyond-the-first-year laboratory classes. At Davidson College, they use Arduinos in a gateway STEM course for students who are interested in energy and the environment. This article describes how students…

In high school, and also in introductory physics courses in higher levels of schooling, the law of universal gravitation of planets is introduced by postulating Johannes Kepler's three laws, and later Isaac Newton's law of the inverse of the square of the distance to the Sun. The justification of the laws is only achieved in advanced courses in…

Scientific laboratories are among the most challenging course components to integrate into online instruction. Available technology restricts the design and nature of experiments, and it can be hard to replicate the collaborative lab environment where frequent and immediate instructor feedback is the norm. Here we report on technological and…

As intriguing optical phenomena that occur in nature, mirages are widely known and often mentioned in physics classes when introducing the basics of optics. In the atmosphere, a mirage occurs under the condition of vertical variations in air density, which are usually caused by a temperature gradient. The light rays are continuously refracted and…

An electric motor converts electrical energy into mechanical work and an electric generator converts mechanical work into electrical energy. The symmetry between the motor and generator naturally leads to questions about creating a perpetual motion machine. The allure of this question has inspired textbook problems, physics education articles, and…