Over the past half-century, numerous attempts have been made to derive the centripetal acceleration formula by treating circular motion as a superposition of uniform and accelerated rectilinear motions over short time intervals. Critical examination reveals that these methods are manifestations of the same approach pioneered by Huygens to…

To explain experiences of riders of rotating systems, such as a merry-go-round, some physics educators have employed the concept of 'centrifugal force.' However, others have suggested that the term is unnecessary in explaining experiences in rotating systems and that it encourages misconceptions surrounding circular motion dynamics. Owing to this…

This study considers the concept of observer--the fundamental concept axial for fundamental physical theories. The history of the observer concept in physics is reviewed and summarized. In the following, the observer concept is considered with regard to science education where scientific concepts should reflect their status in science. This…

The various aspects of projectile motion have been analyzed many times in this journal. As a sample, over the years, authors have investigated particular details of the path of a projectile and different situations for launching projectiles. Others have written about a nifty way to determine the maximum height of a projectile, finding the range of…

Modern MEMs gyros/accelerometers allow the angular velocity of pendula to be precisely measured and the angular acceleration to be calculated. For a compound pendulum, "I"[subscript p][umlaut over theta]=-"mga" sin[theta]Ip[umlaut over theta]=-mgasin[theta], where "a" is the distance of the center of mass from the…

Difficulties in understanding physics concepts are often experienced by students such as in the material of regular uniform motion. This study aims to describe the mental models of first-year secondary school students on regular straight-line motion. This research utilized a case study method of 167 students at the secondary level with an average…

Background: Recognizing the relatively few studies that have explored university students' understanding and alternative conceptions in linear and circular motion as well as the relatively few studies that have used 2-dimensional multiple-choice questions (MCQs) in the science education literature, this study set out to contribute to these areas.…

We describe a simple, intuitively appealing interpretation of the observed ellipsoidal shape of the rotating Earth: it is that surface everywhere perpendicular to the net force upon it.

On 24 June 1994 at Fairchild Air Force Base, during practice for an air show, a low-flying B-52H aircraft banked its wings vertically and crashed. Emphasizing the activity of modeling drag and gravity, these notes examine the possibility of recovery with several models. First, with algebra, historical data lead to a model where in a free fall near…

This paper has a pedagogical aim. Indeed, by using the relativistic velocity-addition and Einstein's equivalence principle (EEP), we want to analyse in a simple way the physics of time on a rotating non-inertial frame. We use a didactic approach considering four friends. The first is in the laboratory, the second at rest on the disk at radius r,…

Acceleration of moving objects is usually measured by photoelectric gates. In this paper, a method of acceleration measurement is proposed by pasting white card stock and black tape on a pulley and then using an Arduino to time the motion. This method only needs one photoelectric sensor to measure the acceleration. In contrast, using photoelectric…

Inspired by a commercially produced scattering experiment that was popular beginning in the 1960s, we have developed a Nerf-projectile-based educational activity to demonstrate the basics of particle scattering experiments.

Over four decades of conceptual change studies in education have been based on the assumption that learners come to science classrooms with functionally fixated intuitive ideas. However, it is largely ignored that such pre-instructional conceptions are probabilistic, reflecting some aspects of an idiosyncratic sampling of their experiences and…

The relativistic addition of velocities is usually introduced early in the study of Einstein's special theory of relativity. The equations are simple enough, but randomly chosen velocities lead to unwieldy calculations that can dishearten the student. This paper presents tables of velocity components in two dimensions, composed of five or fewer…

If an empty coffee cup is spun on a horizontal surface about a vertical axis in an anti-clockwise direction, then the whole cup rotates slowly backwards, in a clockwise direction, about a vertical axis located outside the cup. Clues to this curious behaviour are presented by comparing it with other spinning objects.