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…

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.

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…

The conservation law of energy and momentum can be examined and demonstrated by a well-known collision experiment. In this experiment, several identical elastic balls are suspended from a horizontal frame. When the ball at one end is pulled aside and released, thus allowing it to swing like a pendulum, it hits the next ball. The outcome is…

The author, Greg DeLisi, a professor at John Carroll University, is always looking for ways to bring current events into his introductory physics classroom or laboratory. He is especially interested in finding examples where basic principles of physics can be used to cast skepticism on assertions made by celebrities, politicians, or professional…

Describing the motion in a vertical roller coaster loop requires a good understanding of Newton's laws, vectors and energy transformation. This paper describes how first-year students try to make sense of force and acceleration in this example of non-uniform circular motion, which was part of a written exam. In addition to an analysis of the exam…

Einstein's two theories of relativity were introduced over 100 years ago. High school science students are seldom exposed to these revolutionary ideas as they are often perceived to be too difficult conceptually and mathematically. This paper brings together the two theories of relativity in a way that is logical and consistent and enables the…

The mechanical energy change of a system in an inertial frame of reference equals work done by the total nonconservative force in the same frame. This relation is covariant under the Galilean transformations from inertial frame S to S', where S' moves with constant velocity relative to S. In the presence of nonconservative forces, such as normal…

We describe the kinematics, dynamics, and also some energy issues related to Marta mouse's motion when she walks on top of a horizontal bicycle wheel, which is free to rotate like a merry-go-round, as presented recently by Paul Hewitt in the "Figuring Physics" section of this journal. The situation is represented in Fig. 1, which was…

Newton's first and second laws have implications for the kinetic energy as well as the momentum of a body. It is recommended that this should be made explicit at an appropriate point in a course.

Kinetic energy and momentum are indispensable dynamical quantities in both the special theory of relativity and in classical mechanics. Although momentum and kinetic energy are central to understanding dynamics, the differences between their relativistic and classical notions have not always received adequate treatment in undergraduate teaching.…

The work describes an analogy-based small oscillations analysis of a standard static equilibrium lab problem. In addition to force analysis, a potential energy function for the system is developed, and by drawing out mathematical similarities to the simple harmonic oscillator, we are able to describe (and experimentally verify) the period of small…

For years the fan cart has provided physics students with an excellent resource for exploring fundamental mechanics concepts such as acceleration, Newton's laws, impulse, momentum, work-energy, and energy conversions. "The Physics Teacher" has even seen some excellent do-it-yourself (DIY) fan carts and activities. If you are interested…

This paper presents a brief review of Ising's work done in 1925 for one dimensional spin chain with periodic boundary condition. Ising observed that no phase transition occurred at finite temperature in one dimension. He erroneously generalized his views in higher dimensions but that was not true. In 1941 Kramer and Wannier obtained…