Atoms may repel or attract each other, but bound systems get virtually all of the attention in the classroom. To address the imbalance, instructors can explore the basis of repulsion in a few simple systems and highlight the important role played by the Pauli principle. A good example is the first triplet excited state of H[subscript 2] wherein…

Most physics teachers have observed the majestic swings of a monumental pendulum at a science museum and have watched long enough to see the plane of oscillation slowly changing direction as Earth turns. The purpose of Don Olson's article is to describe visits to Paris sites related to Jean Bernard Léon Foucault (1819-1868), with a special focus…

This paper starts with an introduction to the concept of momentum current. It is followed by a discussion of its strength and density with the aid of several analogies made between momentum current and electric current. Based on the novel concepts of thermal charge and its quantity (entropy), the analogies are extended to entropy current. The…

This study aims to make a thematic classification of possible misconceptions about solid friction by reviewing papers in the literature which include conceptual difficulties about friction; in this way, the study contributes to the literature. The study's scope was limited to the dry friction that occurs with the interaction of two solid objects,…

Chladni patterns are one of the most fascinating physics demonstrations. They can be produced very easily using commercially available apparatus based on metallic plates attached to a mechanical driver, similar to a loudspeaker without the membrane, and a signal generator. The figures are observed using sand sprinkled on the surface of the plate.…

Already when they enter primary school, children have rich everyday experience with factors influencing the rate of liquids' evaporation. Tea spilled into a large puddle on the table evaporates more rapidly than the same amount remaining in the cup, laundry hanging on a clothesline dries faster on a hot and windy day in comparison with a cold and…

At a conference on educational physics, someone described a series of multiple-choice problems to test students' ideas about various mechanical phenomena. One of the problems questioned students' conceptions about the shape of the Earth's orbit in the solar system. The question was as follows: "Which of the following schematic illustrations…

The conventional approach to teaching blackbody radiation in introductory modern physics courses relies on an oversimplified explanation of Wien's displacement law, which does not uphold students' conceptual understanding of Planck's law and can lead to well-known misconceptions. Thus, there is a need to clarify the pedagogical role of this…

In order to describe the velocity of two bodies after they collide, Newton developed a phenomenological equation known as 'Newton's experimental law' (NEL). In this way, he was able to practically bypass the complication involving the details of the force that occurs during the collision of the two bodies. Today, we use NEL together with momentum…

A hula hoop rotating around a person's waist is an example of circular motion where the centripetal force on the hoop is directed towards the centre of the circle rather than the centre of the hoop. The friction force on the hoop is relatively small by comparison since the hoop rolls around the waist. A slight complication is that the hoop rotates…

In an effort to examine students' understanding about the structure of boundary conditions in upper-division courses, think-aloud interviews were conducted in the context of both quantum mechanics and electricity and magnetism. In the quantum mechanics task, students were presented with a standard potential step scenario. In the electricity and…

The Sun is a central feature to the human experience. It is found in many familiar idioms like "nothing new under the Sun." It defines our days, makes our planet habitable, and is the ultimate origin of your last meal. Yet how do we understand how it works?

Observing the bouncing of a marble on a table is a rather common experience. The tic-tac sound of the rigid ball, nevertheless, carries quite a pleasant surprise. In fact, by measuring the total time of bouncing [delta]t, the coefficient of restitution can be estimated. As is well known, in an inelastic collision the kinetic energy is not…

If a ball rolls at constant speed on a horizontal surface about a horizontal axis then the angular velocity is easily measured. If the ball is projected with additional spin about the vertical axis, then the rotation axis is tilted and it is more difficult to measure the rotation speed. A few examples are presented to show how the separate topspin…

Using the analogy between thermodynamics and electricity, two new concepts of thermal charge and quantity of thermal charge are introduced. A simple yet explicit definition of entropy is then derived-entropy is the quantity of thermal charge. As a result, quantity of thermal charge (entropy) and quantity of heat (energy) are now clearly…