Many physics textbooks start with kinematics. In the lab, students observe the motions, describe and make predictions, and get acquainted with basic kinematics quantities and their meaning. Then they can perform calculations and compare the results with experimental findings. In this paper we describe an experiment that is not often done, but is…

In 1879, in the midst of the debate between English and continental scientists about the nature of cathode rays, William Crookes conducted an experiment in which a small mill or "paddle wheel" was pushed along tracks inside a cathode ray tube (CRT) (similar to that shown in Fig. 1) when connected to a high-voltage induction coil. Crookes…

In our science for non-science majors course "21st Century Physics," we investigate modern "Hubble plots" (plots of velocity versus distance for deep space objects) in order to discuss the Big Bang, dark matter, and dark energy. There are two potential challenges that our students face when encountering these topics for the…

One of the very popular demonstrations used in introductory physics courses to illustrate Lenz's law is the "slowly falling magnet." In its simplest version it requires only a powerful cylindrical magnet and a metal tube, typically of copper or aluminum. When dropped in the tube the magnet takes significantly longer to reach the other end than a…

A light-emitting diode (LED) and operational amplifier can be used as an affordable method to provide a digital output indicating detection of an intense light source such as a laser beam or high-output LED. When coupled with a microcontroller, the combination can be used as a multiple photogate and timer for under $50. A similar circuit is used…

The commercial resonance demonstration apparatus shown in Fig. 1 exhibits curious behavior. It consists of three pairs of slender spring-steel rods attached to a horizontal bar. When one of the rods is pulled aside and released, the rod of corresponding length is excited into visible motion, but the other rods remain apparently stationary. This…

Going "green" is a slogan that is very contemporary, both with industry and in the political arena. Choosing more energy-efficient devices is one way homeowners can "go green." A simple method is to change home lighting from hot incandescent bulbs to compact fluorescent lights (CFLs). But do they really save energy? How do their illuminations…

A recent note in this journal presented a demonstration of standing waves along a cord consisting of two parts having different material densities, showing different sized wavelengths in each part. A generalization of that experiment to a continuously varying linear mass density is to vibrate a strip of material with gradually varying width (mass…

Early in the last century, Robert Millikan developed a precise method of determining the electric charge carried by oil droplets. Using a microscope and a small incandescent lamp, he observed the fall of charged droplets under the influence of an electric field inside a small observation chamber. In so doing, Millikan demonstrated the existence of…

This paper presents a laboratory exercise that introduces students to the use of video analysis software and the Lenz's law demonstration. Digital techniques have proved to be very useful for the understanding of physical concepts. In particular, the availability of affordable digital video offers students the opportunity to actively engage in…

When illuminating four "mystery" vials of nanoparticle solution with a 405-nm light emitting diode (LED), four distinct colors related to the peak wavelength of fluorescent emission can be observed. This phenomenon perplexes high school physics students and leads to the subsequent exploratory question, "Why are the four vials emitting a different…

This paper was inspired by the numerous requests from "TPT" readers to expand the number of examples of "recurrent study" lab exercises described in my previous paper "Physics Labs with Flavor." I recommend that readers examine it first in order to better understand this one as my attempt here is to be brief. In that paper, one can find details…

The siphon is a very useful example of early technology, the operation of which has long been well understood. A recent article makes the claim that established beliefs regarding this device are incorrect and proposes a "chain model" in which intermolecular forces within the fluid play a large role while atmospheric pressure does not. We have…

Physics First is offered to ninth graders at high schools in Aurora, CO. A unique new asset of this school system is an embedded research lab called the "Innovation Hyperlab." The goal of the lab is to connect secondary school teaching to ongoing university scientific research, supporting the school district's aim to create opportunities to…

Jay Orear, in his introductory physics text, defined the weight of a person as the reading one gets when standing on a (properly calibrated) bathroom scale. Here we will use Jay's definition of weight in a thought experiment to measure the weight of a photon. The thought experiment uses the results of the Pound-Rebka-Snider experiments, Compton…