The falling rod paradox, i.e. the fact that the tip of an almost horizontal rod falls with an acceleration 'higher than g', when the other end is hinged or supported, is a popular physics demonstration. It can be visualized by placing e.g. a coin on the tip of the rod and fixing a cup next to the coin. When the rod is released the free-falling…

Experimental results are presented concerning a bead sliding on a rotating, horizontal rod. If the rod rotates at constant angular velocity then the sliding speed in the radial direction increases exponentially with time, provided that the rotation speed is sufficient to overcome friction. Otherwise the bead rotates in a circular path of constant…

The contamination of wastewater with metals and the use of biotechnologies to remove them is commonly discussed in theoretical biology, microbiology and biotechnology classes aimed at undergraduate students. This work introduces an easy, economical and safe practical laboratory class related to this topic. The practice consists in performing batch…

Costume jewelry beads are employed to demonstrate how a beam of beads are able to transform into a simple pendulum (single bead) where the pendulum length remains constant throughout. These beads are common and inexpensive for instructors, as well as attractive and exciting for students. Beads are removed from the top, keeping the same pendulum…

Problems involving rotating systems analysed from an inertial frame, without invoking fictitious forces, is something that freshman students find difficult to understand in an introductory mechanics course. In this article we try to see what could be the factors that lead to this difficulty and propose a set of arguments that could be used to…

The motion of a bead along a path restricted to straight lines (restricted brachistochrone), sliding without friction from rest and accelerated by gravity, is considered. For two shapes of path, the geometry of the route optimized to provide the least travel time from one point to another is obtained. The bead's travel times, path lengths, and…

The purpose of this laboratory experiment is to study fundamental concepts of kinetics and equilibria and the isotope effects associated with both of these concepts. The concepts of isotopes in introductory and general chemistry courses are typically used within the contexts of atomic weights and radioactivity. Kinetic and equilibrium isotope…

In this paper, we discuss the theory of the operation and some practical considerations for the construction of an air ionization chamber, which can be used as a very simple detector of alpha particles. These detectors have several benefits compared to spinthariscopes and spark detectors. Classical experiments with ionization chamber detectors are…

At the end of the 18th-century, Charles Coulomb developed an apparatus to study the force between two electrified beads which allowed him to obtain his famous Coulomb's law. Today, as one of the most fundamental outcomes in classical electromagnetism, his result is revisited in most high school physics courses, where students are asked to…

Throughout the general chemistry lab curriculum, a common shortcoming is the way in which students measure, record, and manipulate quantitative data. From initial measurements with different digital and analog instruments to proper conversions, calculations, and comparisons, students are often expected to be experts before they have been taught…

A highly visual, inexpensive, straightforward laboratory experiment for the determination of the activation energy of a demulsification process is presented. The experiment uses low-density polyethylene (LDPE) beads to clearly mark the interface between an NaCl(aq) solution and isopropanol. The NaCl(aq)-isopropanol system is shaken to produce an…

During this activity, by making beaded bracelets that represent the steps of translation, students simulate the creation of an amino acid chain. They are given an mRNA sequence that they translate into a corresponding polypeptide chain (beads). This activity focuses on the events and sites of translation. The activity provides students with a…

Among the efforts directed at remediating contaminated sites, the use of immobilized microorganisms is an appealing alternative because it offers several advantages over the use of free cells, including protecting cells from the toxic effects of hazardous compounds and increasing their survival and metabolic activity. "Pseudomonas…

This paper describes a simple, cost-effective experiment which introduces students to drug delivery and modeling using alginate beads. Students produce calcium alginate beads loaded with drug and measure the rate of release from the beads for systems having different stir rates, geometries, extents of cross-linking, and drug molecular weight.…

Lab-on-a-chip technology is brought into the classroom through development of a lesson series with hands-on practicals. Students can discover the principles of microfluidics with different practicals covering laminar flow, micromixing, and droplet generation, as well as trapping and counting beads. A quite affordable novel production technique…