Energy conversion devices such as fuel cells, metal-air batteries, and electrolyzers have been envisaged as possible solutions for cutting down the continuous accumulation of greenhouse gases resulting from the combustion of fossil fuel. The bottleneck reaction for these devices is the oxygen reduction reaction (ORR) occurring at the cathode. The…

Although the old problem of rotating liquid is described and solved in many textbooks and articles, the story still remains interesting. Intuitive understanding of the equipotential spatial surfaces is very difficult. This article is an attempt to present Newton's rotating tank in the light of the law of conservation of energy.

Teaching special relativity to lower-division students is challenging because results such as time dilation, length contraction, and frame dependence of simultaneity are counterintuitive. The literature is extensive, so only a brief list is given here, with articles divided roughly between discussions of general principles and calculations applied…

Ampère's law is presented in introductory physics as a relation between the line integral of the magnetic field around a closed loop and the net current crossing any open surface spanning that loop. By allowing the surface to pass between the plates of a charging parallel-plate capacitor, Maxwell realized that this law is incomplete and introduced…

In one of the Faraday's experiments an electric current is induced in a conducting loop when a magnet in front of it moves towards or away from the loop. While the direction of circulation of the electric current in the loop has only two options, it depends on three experimental conditions that generate eight cases. Even though the Faraday law or…

Bridges are a popular topic in this journal, because they are a very visual display of static and dynamic physical principles. In this paper, we provide an intuitive derivation of the equations associated with suspension bridge cables and load-bearing arches, which is of pedagogical interest in illustrating the consequences of Newton's laws for…

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…

The calculation of the magnetic field produced by a loop current using the Biot-Savart law is a very typical exercise in introductory university physics. However, the cases studied are limited, in most textbooks, only the circular arrangement is treated. In this article, we calculate the magnetic field of an elliptical loop current along an axis…

Breathing is something we all do, usually without thinking about it. But when viewed through the lens of physics, respiration becomes an example of elementary thermodynamics. As shown here, the lungs can be modeled as a two-stroke heat engine. Breathing thereby provides a novel physics application for life science students, demonstrating the…

The concept of black body is of primary importance in studying the energy transfer of thermal electromagnetic radiation at all wavelengths. Several physical bodies like incandescent lamps, electric heaters, stoves, the sun and the other stars, microwave background radiation, etc., are considered to be black bodies as their radiation spectra fits…

Newton's cradle is often discussed in science classrooms as a clear example of the laws of conservation of momentum and energy although it has been shown that this use is somewhat misleading. Approaches to understanding the behaviour of this apparatus are often over-simplified and deficient or over-complex and with little impact among teachers. In…

When a ball bounces obliquely on a horizontal surface, the bottom of the ball stretches horizontally and then vibrates backward. The resulting ball spin depends sensitively on the transverse vibration frequency. A simple model is presented to describe the effect, showing how the stored elastic energy can result in additional spin.

Archimedes' principle states the buoyant force is equal to the weight of fluid displaced by the object. In this work, we will develop this principle using energy considerations.

A well-known conclusion from elementary ballistic trajectory analysis is that the horizontal range of a projectile is maximized for a launch angle of 45°. The derivation of this result assumes that the launch speed is the same for all possible launch angles, but this neglects the fact that the work done against gravity by the launching mechanism…

Newton's cradle is a well-known physics toy that is commonly used by teachers to demonstrate conservation laws in mechanics. It can also be used to investigate the physics of colliding objects, by recording motion of the balls on video film. Various experiments are described using 3-ball and 5-ball cradles, showing how different types of collision…