Table of contents

A quick and very accessible method for the measurement of acceleration due to gravity is presented. The experimental set-up employs a smartphone ambient light sensor as the motion timer for measuring the period of a simple pendulum. This allowed us to obtain an experimental value, 9.72  +  0.05 m s⁻², for the gravitational acceleration which is in good agreement with the local theoretical value of 9.78 m s⁻².

A probability-based model for estimating the critical mass of a fissile isotope is developed. The model requires introducing some concepts from nuclear physics and incorporating some approximations, but gives results correct to about a factor of two for uranium-235 and plutonium-239.

A way to scaffold students' understanding of abstract physics concepts is through fun activities that help in visualisation. This article highlights a simple flying wheel toy can be used as a demonstration kit in presenting the equation 'Work Done  =  Force  ×  Distance'. The kit has helped the author's students visualise the equation, getting them to appreciate how components of the equation are related to one another, which otherwise may have been abstract for them.

The classic demonstration illustrating Lenz's law by dropping a magnet through a copper pipe is presented using household aluminum foil right out of the box. Then comes the surprise. The teacher presents an aluminum foil cylinder with a missing lengthwise slice (cut before class). Will the demonstration still work? Students are amazed at the result, described in this paper and included in our accompanying video (Ruiz 2018 Video: Lenz's law with aluminum foil http://mjtruiz.com/ped/aluminum/).

Projectile motion is a constant theme in introductory-physics courses. It is often used to illustrate the application of differential and integral calculus. While most of the problems used for this purpose, such as maximizing the range, are kept at a fairly elementary level, some, such as determining the safe domain, involve not so elementary techniques, which can hardly be assumed of the targeted audience. In the literature, several attempts have been undertaken to avoid calculus altogether and keep the exposition entirely within the realm of algebra and/or geometry. In this paper, we propose yet another non-calculus approach which uses the projectile's travel times to shed new light on these problems and provide instructors with an alternate method to address them with their students.

A glass filled with carbon dioxide gas upside down on a plate of water constitutes an excellent demonstration of the solubility of gases. If the water level on the plate is maintained the CO₂ will slowly dissolve and the column of water will rise inside the glass, without quite reaching the ceiling, before an opposite process sets in: the water level will even more slowly begin to sink in a process which will take several years. We followed the process for several months, recording images of the water column with 10 min to 1 h intervals. The physics of the process is discussed and modeled quantitatively.

The French horn is used to introduce the three basic properties of periodic waves: amplitude, frequency, and waveform. These features relate to the perceptual characteristics of loudness, pitch, and timbre encountered in everyday language. Visualizations are provided in the form of oscilloscope screenshots, spectrograms, and Fourier spectra to illustrate the physics. Introductory students will find the musical relevance interesting as they experience a real-world application of physics. Demonstrations playing the French horn are provided in an accompanying video (Ruiz 2018 Video: Amplitude, frequency, and timbre with the French hornhttp://mjtruiz.com/ped/horn/).

In the sport of American football, the quarterback (QB) is the player almost always responsible for throwing the ball downfield to an open receiver. That important throw requires him to make a split second decision to launch the ball at the correct speed and angle to guarantee it lands directly into the hands of the receiver. In this paper we model the decision for two cases. The authors first consider the case of a receiver running at constant acceleration and find that, for a successful throw, the ball's launch angle depends only on the receiver's constant acceleration while the ball's initial speed is not a factor. Secondly, the article discusses the more realistic case of a receiver running at a variable acceleration showing that the QB can perform a successful throw for various angle/ball's initial speed combinations in which the angle and speed are approximately linearly related.

In this article, we describe how to develop an inductive metal detector that can be integrated to any Android or iOS smartphone with a standard audio port at low cost. The results indicate the metal detector can be used in the physics teaching laboratory as a practical application of principles of electromagnetism. It allows one to differentiate ferromagnetic samples from the diamagnetic and paramagnetic ones and can also be used to investigate the direction of alternating magnetic fields and to demonstrate the Faraday's cage shielding effect.

Propagation of sound waves is one of the fundamental concepts in physics. Some of the properties of sound propagation such as attenuation of sound intensity with increasing distance are familiar to everybody from the experiences of daily life. However, the frequency dependence of sound propagation and the effect of acoustics in confined environments are not straightforward to estimate. In this article, we propose experiments, which can be conducted in a classroom environment with commonly available devices such as smartphones and laptops to measure sound intensity level as a function of the distance between the source and the observer and frequency of the sound. Our experiments and deviations from the theoretical calculations can be used to explain basic concepts of sound propagation and acoustics to a diverse population of students.

A compact Lecher Line apparatus (21 cm in length) has been constructed. Standing waves can be demonstrated when different terminations are added to the line and these allow the frequency of the radiation to be determined. By having Phase Detection permittivity values of liquid or granular materials can be determined. As an example, the permittivity of granular sugar was found to be 1.9 (±0.2).

The sensors in modern smartphones are a promising and cost-effective tool for experimentation in physics education, but many experiments face practical problems. Often the phone is inaccessible during the experiment and the data usually needs to be analyzed subsequently on a computer. We address both problems by introducing a new app, called 'phyphox', which is specifically designed for utilizing experiments in physics teaching. The app is free and designed to offer the same set of features on Android and iOS.

is a hollywood action film ( official film site: www.skyscrapermovie.com) directed and written by Thurber scheduled to be released on 13 July 2018. We present an analysis of the feat shown in the recently released teaser poster and trailer of the film. Although the feat appears to be unrealistic at first glance, after close investigation using back-of-the-envelope calculations, it is seen to be within human capabilities.

In 2016, we (seven high school students from a school in Plock, Poland) participated in the CERN Beamline for Schools competition. Together with our team coach, Mr. Janusz Kempa, we submitted a proposal to CERN that was selected as one of two winning proposals that year. This paper describes our experiment from the early days of brainstorming to the trip to Geneva.

We present an educational game for teaching physics, Spies. The game is based on the popular boardgame Codenames. It is useful as a didactic tool to promote and improve student engagement. Spies is practical, fast and requires very little physical resources, which makes it ideal for high school teaching and viable in most diverse school realities.

To introduce the randomness of a physical process to students, a chaotic pendulum experiment was opened in East China University of Science and Technology (ECUST) on the undergraduate level in the physics department. It was shown chaotic motion could be initiated through adjusting the operation of a chaotic pendulum. By using the data of the angular displacements of chaotic motion, random binary numerical arrays can be generated. To check the randomness of generated numerical arrays, the NIST Special Publication 800-20 method was adopted. As a result, it was found that all the random arrays which were generated by the chaotic motion could pass the validity criteria and some of them were even better than the quality of pseudo-random numbers generated by a computer. Through the experiments, it is demonstrated that chaotic pendulum can be used as an efficient mechanical facility in generating random numbers, and can be applied in teaching random motion to the students.

In this paper we present a critical analysis of some of the arguments of flat Earth theory, and we also try to show that this analysis and refutation of these false claims can be a useful exercise in critical thinking that is so much needed today. This article can also make it easier for teachers who are exposed to some of the arguments of flat Earth theory by their students. Some arguments of this theory are completely senseless, and some can simply be disproved by trigonometry or basic physical laws.

Lecturer-researchers, because of the duality of their profession, can introduce students directly to their research. Stimulating student interest through practical research topics enables students to see the relevance of the teaching/learning process and thereby enhance their motivation. As a major societal issue, research on renewable energies is held in great esteem, particularly among young students with a strong interest in environmental issues. The work presented here relates to the realization of a practical class on the testing of a flexible piezoelectric generator studied as part of the 'N-air-J' regional research project. The particular characteristic of piezoelectric materials is that they produce electricity when compressed, which means that they can be used in energy recovery devices. The electrical model associated with this type of generator, consisting of an ideal current source in parallel with a linear capacitor and a load resistor, is sufficiently simple to understand following a course on electricity for first-year university students. High school students in their first year of a science and laboratory technology baccalaureate in France have already taken this practical class as part of a dissemination campaign on scientific culture.

SenseCube is a multisensor capable of measuring many different real-time events and changes in environment. Most conventional sensors used in introductory-physics labs use their own software and have wires that must be attached to a computer or an alternate device to analyze the data. This makes the standard sensors time consuming, tedious, and space-constricted. SenseCube was developed to overcome these limitations. This research was focused on developing a device that is all-encompassing, cost-effective, wireless, and compact, yet can perform the same tasks as the multiple standard sensors normally used in physics labs. It measures more than twenty distinct types of real-time events and transfers the data via Bluetooth. Both Windows and Mac software were developed so that the data from this device can be retrieved and/or saved on either platform. This paper describes the sensor itself, its development, its capabilities, and its cost comparison with standard sensors.

An amusement park is full of examples that can be made into challenging problems for students, combining mathematical modelling with video analysis, as well as measurements in the rides. Traditional amusement ride related textbook problems include free-fall, circular motion, pendula and energy conservation in roller coasters, where the moving bodies are typically considered point-like. However, an amusement park can offer many more examples that are useful in physics and engineering education, many of them with strong mathematical content. This paper analyses forces on riders in a large rotating pendulum ride, where the Coriolis effect is sufficiently large to be visible in accelerometer data from the rides and leads to different ride experiences in different positions.

Although infinite potential 'particle in a box' models are widely used to introduce quantised energy levels their predictions cannot be quantitatively compared with atomic emission spectra. Here, this problem is overcome by describing how both infinite and finite potential well models can be used to calculate the confined energy levels of semiconductor quantum wells. This is done by using physics and mathematics concepts that are accessible to pre-university students. The results of the models are compared with experimental data and their accuracy discussed.

In this work we present a simple and low-cost setup to illustrate the dependence of the behaviour of a standing wave in a guitar string with the initial conditions. To do so, we impose two kinds of initial conditions; in the first instance, the initial shape of the string is varied. Secondly, different nodes are imposed on the string. This dependence was studied using the Fourier analysis of the sound produced by the vibration of the string with a smartphone. The simplicity of the proposed activity makes it suitable to be implemented in any classroom to illustrate the concept of normal modes and as an example of Fourier series in a real system that is also familiar for the students.

To improve the teaching and learning materials for a curriculum it is important to incorporate the findings from educational research. In light of this, we present creative exercises and experiments to elicit, confront and resolve misconceptions in geometrical optics. Since ray diagrams can be both the cause and the solution for many misconceptions we focus strongly on improving understanding of this tool to solve and understand optical phenomena. Through a combination of a conceptual understanding programme (CUP) and provocative exercises with ray diagrams we aim to elicit conceptual or cognitive conflict and exploit this to tackle misconceptions and increase students' conceptual understanding through inquiry. We describe exercises for image formation by a plane mirror, image formation by a convex lens and indirect and direct observation of a real image formed by a convex lens as examples of our approach.

This work deals with the experimental demonstration of coupled oscillators using simple tools in the form of mechanical coupled pendulums, magnetically coupled elastic strings or electromagnetic oscillators. For the evaluation of results the data logger Lab Quest Vernier and video analysis in the Tracker program were used. In the first part of this work, coupled mechanical oscillators of different types are shown and the data analysis by the Tracker or Vernier Logger Pro programs. The second part describes a measurement using two LC circuits with inductively or capacitive coupled electromagnetic oscillators and the obtained experimental results.

This research proposes the development of a web-based assessment system to identify students' misconception. The system, named WAS (web-based assessment system), can identify students' misconception profile on linear kinematics automatically after the student has finished the test. The test instrument was developed and validated. Items were constructed and arranged from the result of a focus group discussion (FGD), related to previous research. Fifty eight students (female  =  37, male  =  21) were used as samples. They were from different classes with 18 students from the gifted class and another 40 students from the normal class. WAS was designed specifically to support the teacher as an efficient replacement for a paper-based test system. In addition, WAS offers flexible timing functionally, stand-alone subject module, robustness and scalability. The entire WAS program and interface was developed with open source-based technologies such as the XAMP server, MySQL database, Javascript and PHP. It provides results immediately and provides diagrammatic questions as well as scientific symbols. It is feasible to apply this system to many students at once. Thus, it could be integrated in many schools as part of physics courses.

The article proposes a new research object for a general physics course—the vapour Cartesian diver, designed to study the properties of saturated water vapour. Physics education puts great importance on the study of the saturated vapour state, as it is related to many fundamental laws and theories. For example, the temperature dependence of the saturated water vapour pressure allows the teacher to demonstrate the Le Chatelier's principle: increasing the temperature of a system in a dynamic equilibrium favours the endothermic change. That means that increasing the temperature increases the amount of vapour present, and so increases the saturated vapour pressure. The experimental setup proposed in this paper can be used as an example of an auto-oscillatory system, based on the properties of saturated vapour. The article describes a mathematical model of physical processes that occur in the experiment, and proposes a numerical solution method for the acquired system of equations. It shows that the results of numerical simulation coincide with the self-oscillation parameters from the real experiment. The proposed installation can also be considered as a model of a thermal engine.

In 2017, almost everywhere in the world, there was a boom in sales of fidget spinners. A toy that has 'multi-lobes' that can rotate freely from a thrust performed with the fingers. Thereby, we analysed the physics concepts that involved in this toy, such as angular and linear velocity. We did the analysis using the software Tracker, a laboratory light sensor, a free mobile application that turns the device flashlight into a strobe light source. Thus, we aim to show that it is possible to transform a well-known toy into an opportunity to work on physics concepts and to construct experiments in the classroom.

In a recent paper, Wang (2017 Phys. Educ. 52 065019), a comparison was made between the efficiency in charging a capacitor (C) in series with a resistor (R) using either a voltage source or a constant current source. The paper concluded that using a current source was more efficient. We show that this is not correct when the energy loss within the current source is considered. It is also shown that the energy loss is not dependent on the charging rate. A formal proof using calculus and simpler graphical arguments are presented.

The recent comment on the paper (Wang 2017 Phys. Educ. 52 065019) attempts to show that the energy loss involved in charging a RC circuit is independent of the charging rate if the loss within the current source is considered. In this reply, the transistor-based control circuit is examined in more detail to reveal the mistake made in the analysis used in the comment. This reply demonstrates that there are additional energy contributions by the control, and, consequently, the total energy loss does depend on the charging rate and the waveform used.

In my article (Featonby 2018 Phys. Educ. 53 037002) we asked what happens when two objects connected by elastic are held vertically, so that the elastic is stretched, and dropped. Which object reaches the ground first.

What happens when a semi inflated Japanese kamifusen, or paper balloon, is bounced in the hand or passed from one person to another?