In this work, a simple rocking pendulum, in a circular arc shape, is presented. The idea is to put a rigid arc on a clean flat surface of glass and leave it to oscillate under the effect of a little impulse. Then, the periodic time of this arc pendulum's motion is experimentally determined. The mathematical analysis of the arc's motion is derived…

We report on an investigation of student thinking about steady-state pipe flow of an incompressible fluid. About 250 undergraduate engineering students were given a test consisting of two hydrodynamics questions, combining multiple-choice format with subsequent open-ended explanations. There is substantial evidence that students have difficulty…

The principles of chemical kinetics comprise one of the core topics that appear throughout chemistry. Standard kinetics lessons typically cover reaction rates and relative rates, rate laws, integrated rate laws, half-lives, collision theory, and the Arrhenius equation. They can also introduce a discussion of mechanisms as well, which may be the…

Most rockets convert the energy stored in their propellant mass into the mechanical energy required to expel it as exhaust. The 'rocket equation', which describes how a rocket's speed changes with mass, is usually derived by assuming that this fuel is expelled at a constant relative velocity. However, this is a poor assumption for cases where the…

Models that are used to predict and explain phenomena related to molecular vibration and rotation are ubiquitous in physical chemistry, and are of importance in many related fields. Yet, little work has been done to characterize student use and application of these models. We describe the results of a multi-year, multi-institutional qualitative…

A cylinder rolling down an inclined board is a commonly seen and interesting object to study and it is also easy to experiment with and model. Following what has become a popular practice, we use smartphones to measure the angular acceleration of a cylinder rolling down a plane of different inclining angles. The friction force deviates from the…

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.…

Context-based learning (CBL) is advocated as beneficial to learners, but more needs to be understood about how different contexts used in courses influence student outcomes. Gilbert defined several models of context that appear to be used in chemistry. In one model that achieves many criteria of student meaning-making, the context is provided by…

First order processes are of paramount importance for chemical kinetics. In a well-established demonstration experiment, the flow of water out of a vertical glass tube through a capillary simulates a chemical first order process. Here, a digital version of this experiment for lecture hall demonstrations is presented. To this end, water flowing out…

We present an educational approach to the phenomenon of phosphorescent emission. The approach is based on a stochastic toy model, in which electron states are represented by rows of squares on a cardboard table, and coins on the squares switch from one row to the other based on the roll of two dice. The discussion of different mechanisms, giving…

The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…

In nonrelativistic quantum mechanics, the total (i.e. orbital plus spin) angular momentum of a charged particle with spin that moves in a Coulomb plus spin-orbit-coupling potential is conserved. In a classical nonrelativistic treatment of this problem, in which the Lagrange equations determine the orbital motion and the Thomas equation yields the…

The paper is about the appearance of space charge in an ohmic conductor moving in a magnetic field, as pointed out in this journal by Lorrain (1990 "Eur. J. Phys." 11 94-8) and earlier by van Bladel (1973 "Proc. IEEE" 61 260-8). The phenomenon is reinvestigated here in the light of energy balance considerations, in the particular case of a…

A modified recipe for the Briggs-Rauscher oscillating reaction is suggested. The modified recipe, [H[subscript 2]SO[subscript 4]] = 0.10 M, [KIO3] = 0.020 M, [NaIO[subscript 4]] = 0.00062 M, [malonic acid] = 0.050 M, [MnSO[subscript 4]] = 0.0067 M, [H[subscript 2]O[subscript 2]] = 1.0 M with 0.01% starch, turns blue almost immediately, then…

I will propose here a kinematic approach for measuring the drag coefficient of rotational symmetric objects falling through liquids. For this, I will show that one can obtain a measurement of the drag coefficient of a rotational symmetric object by numerically solving the equation of motion describing its fall through a known liquid contained in a…