The natural development of static lower limb varus/valgus alignments during early childhood is well understood. However, our understanding of dynamic lower limb frontal plane alignments is limited, and we lack normative descriptions of this phenomenon for both boys and girls. This study investigated dynamic lower limb alignment during…

The dynamics of yo-yo motion are considered in this article. Many textbooks have examined the "rolling" motion of a yo-yo as it moves vertically up or down. However, in the vicinity of the lowest point, a jerk in the string occurs as the center of mass transitions from a linear motion to a pure rotational motion (with respect to the end…

This article describes the newly developing form of poetic duets in Libras (Brazilian Sign Language). What do the two people performing a sign language duet poem do to make a duet different from a solo poem? How can we categorize their actions and the effects that these actions create? Drawing on examples of duet poems in Libras, we analyze…

The question of the sources of electric and magnetic fields and their causes has been discussed extensively in the literature over the last decades. In this article, we approach this problem from the unified treatment of electromagnetic fields emphasizing the role of their sources in accordance with the cause-effect relationships. First, we…

The purpose of this study was to explore the potential of capture systems in improving high school students' dancing skills through the use of experimental design. The major findings were as follows: First, using a MoCap system and high-speed camera to document dancers' movements can provide reference materials for students to improve their skills…

The variation of the period of oscillation of a pendulum with the amplitude is known as "circular error" to clockmakers, and can easily be observed even without modern laboratory instruments. There have therefore been many approximate formulae for the pendulum period as a function of the amplitude, but the simple equation due to Denman,…

In this note, the classical Doppler shift for some accelerated mechanical systems is considered under a common graphical approach. In one dimension, we study uniform accelerated motion and simple harmonic motion. In two dimensions, uniform circular motion and pendular motion are considered. In each case, an elementary treatment shows that the…

Friction is one of the most important forces studied in classical mechanics, and still is the subject of pedagogical literature. In a small series of problems stated below, we consider a particle sliding down a curve under the actions of gravity and kinetic friction. Unlike many of the referenced sources, we neglect the centripetal force arising…

Words influence cognition well before infants know their meanings. For example, three-month-olds are more likely to form visually based categories when exemplars are paired with spoken words than with sine-wave tones, a likely precursor to learning symbolic relations between words and their referents. However, it is unclear why words have these…

There is a close connection between simple harmonic motion and uniform circular motion. This connection is widely taught and included in standard textbooks. Here, we exploit this connection to simultaneously derive two results from introductory mechanics: the period of a mass-spring system and the centripetal acceleration formula. Previously…

As smartphones have become a part of our everyday life, their sensors have successfully been used to allow data acquisition with these readily available devices in a variety of different smartphone-based school experiments. Such experiments most commonly take advantage of the accelerometer and gyroscope. A less frequently used sensor in…

Atwood invented a machine in the 1780s that enabled him to observe the motion of a falling body as slowly as desired. This machine was equipped with the necessary means to measure the distance covered by the body and the time taken. With this data, it was possible, in addition to studying the falling motion, to calculate the local gravitational…

In this paper, we utilize the readily known theory of the ideal transformer to furnish a self-contained qualitative explanation on the AC-powered Thomson jumping ring (TJR) experiment.

Problems involving chains, cables, or ropes that are dropped, folded, or pass around pulleys attract ongoing interest, in part because they can become variable-mass situations if the chain is partitioned into sections for analysis. Less attention has been paid to trying to intentionally project the end of a string as far as possible. Here we…

The trajectory of a ball in air is affected by aerodynamic drag and lift. In general, the trajectory needs to be calculated numerically since the acceleration varies with time in both the horizontal and vertical directions. If the trajectory remains approximately parabolic, then simple analytical solutions can be found, giving useful insights into…