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…

During elementary physics courses, many examples in mechanics are studied without considering air resistance effects. We can mention, for example, projectile motion and free fall, among many others. Only brief studies of such systems in classical mechanics courses consider linear air resistance (F[subscript drag] [is proportional to] v), which is…

On April 14, 1912, the British passenger liner R.M.S. "Titanic" struck an iceberg. The ship sank in a fraction of the time designers had estimated following a worst case scenario. The purpose of this article is to examine the atmospheric refractive phenomena that might have played a significant role in obscuring the iceberg from…

Races between moving objects are an engaging way to teach dynamics to introductory physics students. One standard example consists in racing hollow and solid cylinders as they roll down an inclined plane. Another striking demonstration is a race between two marbles on side-by-side tracks that start and end together, but with one track taking a…

Perhaps the most commonly cited student idea about forces in the literature is the notion of an impetus force, defined as the "belief that there is a force inside a moving object that keeps it going and causes it to have some speed," that can then "fade away as the object moves along." According to the literature, even after…

To a student in introductory physics, using vectors is at best an exercise in bookkeeping. A two-dimensional kinematics problem effectively doubles the number of equations that a student must know, and invites the student to memorize factoids: "The horizontal motion is constant," "Gravity is only in the y-direction," etc. Force…

When deriving the equation describing the transverse motion of a one-dimensional vibrating elastic string, introductory physics textbooks often assume constant tension and/or small amplitude vibrations. However, these simplifying assumptions are not only unnecessary, but they overlook the elastic nature of the tension and yield an inconsistent…

Calculating the duration of a motion when the applied net force on the moving body changes with time is usually a challenging task. In most cases, the only example of the duration of a motion when the acceleration is not constant presented to introductory physics students worldwide is the example of harmonic motion. A discussion with respect to…

The law of conservation of momentum is a fundamental law of nature. It states that the momentum of an isolated system is conserved. In high school or introductory-level physics courses, for simplicity, teachers and textbooks always use collisions in one dimension as the examples to introduce the concept of conservation of momentum. To solve simple…

A common homework problem in many introductory physics courses is similar to the following. "A car drives at constant speed over a hill on a road in the shape of a vertical circular arc. What is the maximum speed the car can have and not lose contact with the road at the crest of the hill?" Unfortunately this problem is flawed, because…

In our first-semester introductory physics laboratory, we have an exercise on rotational dynamics. We have recently upgraded the equipment that we use in that exercise without changing the actual exercise. The new equipment has performed well so far, and we wanted to share what we did with others who may be looking for a relatively inexpensive way…

This study sought to develop and evaluate an online module based on inquiry learning with digital laboratories, which was intended to address students' misconceptions in a science domain. In a quasi-experimental design, 171 first-year students in a higher education introductory physics course on circular motion were as their existing groups…

A rocket in free space accelerates from rest by continuously expelling fuel; as its speed increases, its mass decreases. At what speed (and remaining mass) does the rocket carry maximum momentum? Maximum kinetic energy? The answers provide insights into the dynamics of variable-mass systems, and have applications to planetary defense that are…

The ballistic pendulum apparatus is a fairly ubiquitous element of the introductory physics laboratory, as the pendulum and launcher gun can be used together or independently to demonstrate a variety of concepts from conservation laws to projectile motion to the motion of a physical pendulum. In this work, we control the launch speed of the gun to…

In a 1993 book review, E. Pearlstein asks, "Why don't textbook authors begin their discussion of magnetism by talking about magnets? That's what students have experience with." A similar question can be asked, "Why don't professors have students measure the force between permanent magnets in introductory physics labs?" The…