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,…

The purpose of this publication is to present a novel approach to the demonstration of the Dzhanibekov effect. The main idea of our version is to use a lightweight spinning top of a spherical external form but distinct principal moments of inertia floating in the upward flow of air. As a result, the Dzhanibekov effect can be easily demonstrated…

If a smooth ball is dropped vertically without spin on a smooth horizontal surface then one might expect the ball to bounce vertically without spin. If it does not then the centre of mass of the ball does not coincide with its geometric centre. An experiment is described where a billiard ball and a superball are deliberately biassed by adding a…

Even though many physics teachers take their students on a calculation adventure through circular motion and Newton's universal law of gravity to determine Earth's velocity, most of us leave it at that. We present the final result and say, "Look, Earth is moving around the Sun at about 107,000 km/hr (66,000 mph), yet we can't feel the motion…

As an introduction to sound and vibration, the authors wanted their first-grade students to plan and conduct their own investigations. In this article, the authors share a series of investigations to help students explore the relationship between sound and vibration. By planning, creating, testing, adapting, and reflecting on the outcomes of the…

It is well known that Newton's work on mechanics depended in a crucial way on the previous observations of Galileo. The key insight of Galileo was that one can analyze the motion of bodies using experiments and mathematical equations. One experimental observation that roughly emerges from this work in modern terms is that two objects of different…

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 tidal forces generated by a black hole can be so powerful that they cause unlimited stretching, known as spaghettification. A detailed analysis of this phenomenon requires the use of Einstein's theory of general relativity. The aim of this paper is to offer an up-to-date and accessible analysis of spaghettification, in which the complex…

In high school, and also in introductory physics courses in higher levels of schooling, the law of universal gravitation of planets is introduced by postulating Johannes Kepler's three laws, and later Isaac Newton's law of the inverse of the square of the distance to the Sun. The justification of the laws is only achieved in advanced courses in…

Newton's laws are essential for understanding causes and description of mechanical motion. Great attention is paid to them during physics education. Unfortunately, many students, not only in high school, but also undergraduates, can recite them but do not understand their essence. Therefore, it is useful to demonstrate different experiments in the…

The classic brachistrochrone problem is standard material in intermediate mechanics. Many variations exist including some accessible to introductory students. While a quantitative solution isn't feasible in introductory classes, qualitative discussions can be very beneficial since kinematics, Newton's laws, energy conservation, and motion along…

While the three laws of conservation of energy, momentum, and angular momentum are all mentioned in introductory textbooks, there are few experiments through which students can investigate the conservation of angular momentum. Most experiments consist of collisions between rotating disks, in which one disk is dropped on another, or in which the…

We propose an experimental analogy to verify Kepler's second law using a spherical pendulum. We made a movie of a closed elliptical orbit of the pendulum and extracted the data position using the Tracker software. Analyzing the data, we measured the areas that the position vector sweeps showing the validity of Kepler's second law.

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.