guy's work


title description rating post date author
Stacked Ball Drop - Lessons in Conservation of Energy and Momentum

Drop a stack of balls on the floor. By carefully choosing the relative masses of the balls, it is possible to send the top ball flying many times higher than the distance it fell. Analysis of the collision offers good lessons in relative motion and the conservation of momentu...

Average: 4.3 (72 votes)
20 Jul 2015 guy Ball Drop
Smoke Ring Machines and Dolphin Bubbles

Smoke rings offer wonderful lessons in fluid dynamics. Use them to initiate discussions on fluid flow, air pressure, and Bernoulli's principle. This lesson contains instructions for how to build your own smoke ring machine out of an empty soda bottle, and outlines the physics...

Average: 4 (6 votes)
13 Jun 2014 guy vortex chamber
Motion-induced Blindness Illusions

Motion induced blindness illusions use apparent background motion to make static portions of the visual field temporarily disappear from view. They produce an effect that seems similar to the blind spot in the eye, or the disappearance of images in Cheshire cat illusions, but...

Average: 3.4 (87 votes)
6 May 2014 guy motion blindness illusion
A Survey of Homemade Batteries

A general overview of battery chemistry and operation, with examples of several types of homemade batteries. Tables of suggested materials and sources are included.

Average: 4.4 (33 votes)
15 Apr 2014 guy Coke can battery
Balancing Forks - A Study in Center of Mass

Two forks and a pair of toothpicks are all you need to perform an amazing balancing act (figure 7). Use this demonstration to teach students the fundamentals about "center of mass". A basic tutorial on center of mass concepts is included. Lecture slides are attached.

Average: 4.4 (7 votes)
7 Apr 2014 guy forks and salt shaker
Tabletop Flaming Hurricane

This experiment demonstrates the basic features of hurricanes and tornadoes in spectacular fashion. With a kitchen turntable or a spinning stool, it can be put together with common classroom materials. A tutorial on hurricanes is included. Lecture slides are attached.


Average: 4.3 (3 votes)
31 Mar 2014 guy flaming vortex
Desk Chair Angular Momentum

Describes a simple demonstration of angular momentum conservation using a spinning desk chair. A short tutorial of angular momentum and angular momentum conservation is included.

Average: 4.5 (2 votes)
25 Mar 2014 guy
Vortex in a Bottle

Instructions for building the vortex in a bottle, a device that produces a vortex like the one found in a bathtub drain. The device is completely self-contained and can be used in any classroom setting. It is simple enough and cheap enough for students to build their own to t...

Average: 4.8 (5 votes)
25 Mar 2014 guy vortex in a bottle
Seeing Blood Vessels in the Eye

Describes a technique for seeing the shadows of blood vessels in your eye. Provides a great opportunity for discussing the anatomy of the eye. Requires a dark place.

For more examples of optical illusions caused by visual desensitization, check out our summary curriculu...

Average: 4 (5 votes)
21 Mar 2014 guy retina shadows

This lesson describes how to construct a simple siphon and gives a general tutorial on how siphons work. Lecture slides with extra figures are attached.

Average: 3 (3 votes)
11 Mar 2014 guy siphon with pressure
Slow Motion Magnets

Drop a strong magnet through a copper pipe and watch it slow down as it enters the pipe. The invisible drag is caused by forces between the pipe and the magnet, induced according the laws of electromagentism. It's a magical demonstration for a class, made even better if the s...

Average: 3.7 (3 votes)
3 Mar 2014 guy slow motion magnet
Pendulum Waves

This lesson outlines the construction and operation of a pendulum wave machine that can be built from inexpensive materials in the classroom. Building the demonstration requires a fair amount of patience: construction only takes about 30 minutes, but adjustments and fine tuni...

Average: 4.3 (30 votes)
2 Mar 2014 guy Pendulum Wave
Measuring the Density of Pennies

This activity provides a detailed lesson in measurement and measurement errors, which can be adapted to many different age groups, starting with any group that knows a little bit of geometry (specifically, how to calculate the volume of a disk). The focus of the lesson is on...

Average: 3.5 (36 votes)
23 Feb 2014 guy magnified penny
Homemade Micrometer

This lesson describes how to construct a simple and inexpensive micrometer that can be used to measure objects up to several centimeters thick. It has a readout accuracy of 0.1mm or better, with a potential precision of 0.01mm. Construction time is about 30 to 60 minutes plus...

Average: 4.9 (7 votes)
10 Feb 2014 guy homemade micrometer
Phone Book Friction

It is possible to shuffle two phone books together in a way that they will withstand thousands of pounds of force to pull them apart. This lesson shows an example with discussion of the general principles.

Average: 4.3 (6 votes)
21 Dec 2013 guy
Bernoulli's Balloon

Bernoulli's principle states that a region of fast moving fluid exerts less pressure on its surroundings than a region of slow moving fluid. This principle explains a clever trick for blowing up a long thin balloon in a single breath. Stage a friendly competition in class and...

Average: 4.1 (7 votes)
18 Dec 2013 guy Bernoulli mouth
Bernoulli's Beach Ball

This lesson describes how to float a beach ball on a stream of air. The exercise makes for a magical demonstration in front of a large audience or a lot of fun in an office full of paper. Use it to teach the concept of Bernoulli's principle, which describes the relation betwe...

Average: 4.2 (5 votes)
17 Dec 2013 guy
Benham's Top

In 1894, Charles Benham invented a top with a black and white pattern that produces a sense of color when it spins. This lesson contains instructions and materials for producing your own Benham top, as well as a short explanation behind the false color perception.


Average: 4 (1 vote)
3 Dec 2013 guy
Blind Spot

A description and explanation of the blind spot in the human eye, including exercises for finding and mapping your own blind spot. These exercises work very well on a computer display, and moderately well on a projector screen in front of a class. Lecture slides with images a...

Average: 3.8 (4 votes)
10 Oct 2013 guy
Bernoulli's Principle and the Venturi Tube

The Bernoulli principle states that a region of fast flowing fluid exerts lower pressure on its surroundings than a region of slow flowing fluid. The principle applies to the motion of air over an airplane wing, to air flow through a carburetor, to a flag flapping in the bree...

Average: 4.2 (90 votes)
2 Oct 2013 guy
Soda Bottle Rocket

This lesson gives instructions for a simple rocket that can be constructed out of a soda bottle and some alcohol in a matter of seconds. I also explain the basic principles of rocket propulsion (Newton's 3rd law) and offer some suggested design refinements, including a remote...

Average: 3.8 (10 votes)
15 Sep 2013 guy alcohol rocket
Super Absorbent Polymers - Diapers and Instant Snow

Superabsorbent polymers (SAP's) are used to absorb and retain liquid in a variety of applications, including baby diapers and potting soil. One common SAP, known commercially as "instant snow", is sold as a white powder that can absorb several hundred times its weight in wate...

Average: 4.5 (22 votes)
3 Sep 2013 guy baby with diaper
Cohesion and Surface Tension

Surface tension explains why dew drops are spherical, why a stream of liquid separates into droplets as it falls, and why some heavier-than-water objects can float on the surface of a still pond. In the absence of gravity, surface tension can be a powerful effect, as astronau...

Average: 4.1 (20 votes)
2 Sep 2013 guy water strider
Upside-down Water

Turn a glass of water upside down without letting the water fall out. The secret to this trick involves some basic lessons in air pressure. Best performed over a teacher's head.

Average: 4.3 (155 votes)
13 Aug 2013 guy forces on the upside-down water glass
Homemade Headphones from Picnic Supplies

This lesson provides instructions for building a pair of headphones (or speakers) out of inexpensive materials. It makes for a good science project lasting several hours or a quick demonstration in class if you are willing to build ahead of time, though for a single demonstra...

Average: 2.7 (6 votes)
12 Aug 2013 guy homemade headphones
Earth's Magnetic Field

This lesson gives some information on Earth's magnetic field: the physics of how it is produced and its geologic history. Many suggestions for further reading are also listed. It might be considered useful background for any activity having to do with magnetic compasses. Lect...

Average: 5 (3 votes)
29 Jul 2013 guy history of the north magnetic pole
Battery Basics

This lesson provides general background on the makeup, chemistry, and operation of batteries. Lecture slides attached.

Average: 4.3 (4 votes)
20 Jul 2013 guy batteries in parallel
Lilac Chaser Illusion

The Lilac Chaser illusion is a creation by Jeremy Hinton that relates to the effects of desensitization (and afterimages), motion-induced blindness, and beta movement (perceiving motion from static images). It makes a great follow-up activity after a lesson on negative afteri...

Average: 3.7 (14 votes)
19 Jun 2013 guy Lila Chaser
The Thaumatrope

This lesson contains plans and materials for constructing a thaumatrope, a Victorian era animation toy that blends two images together by making use of human persistence of vision. All that's needed is an index card and some string.

Average: 5 (1 vote)
10 Jun 2013 guy vitruvian geek thaumatrope
Zoetropes, Phenakistoscopes and Other Animation Toys

A lesson on zeotropes, phenakistoscopes and other vintage animation technologies, with explanations and attached printouts for making your own version.


Average: 3.4 (8 votes)
8 Jun 2013 guy zoetrope
Flip Books

A lesson on flip books, with an attached book to print out and pointers on how to make your own flip book.

Average: 4 (1 vote)
3 Jun 2013 guy sciphile detonated
Anatomy of the Eye

This lesson provides an overview of the anatomy of the eye and suggests several simple activites for exploration, including

  • observing pupil response to variations in light
  • verifying the inverted image on the retina
  • comparing central and peripheral v...
Average: 3 (2 votes)
8 May 2013 guy diagram of eye
Positive Afterimages

This lesson contains a short explanation of positive afterimages and some suggestions on how best to see them.

When light shines on the retina, chemical and electrical signals are sent to the brain, providing the basis for our sense of vision. When the light is turned o...

Average: 3.9 (18 votes)
8 May 2013 guy
Color Perception

This lesson provides a tutorial in color perception and the physiology of color sensitive cells in the eye. It includes three classroom activites for exploring color vision:

  1. a game testing peripheral color vision
  2. a demonstration of mixing colored light usin...
Average: 5 (2 votes)
8 May 2013 guy photoreceptor response
Yang and Yin - negative afterimages

This lesson provides a tutorial on the mechanism behind negative afterimages, and includes three afterimage illusions for demonstration. Lecture slides are attached with all images.

For more examples of optical illusions caused by visual desensitization, check out our s...

Average: 3.7 (3 votes)
8 May 2013 guy Mona Lisa negative
Cheshire Cat Illusions

Cheshire cat illusions are images that fade slowly away as you stare at them. They result from desensitization in the eye (and brain) when you view them without moving your eyes. This lesson explains the mechanism behind the disappearance, and provides several examples of opt...

Average: 3.8 (5 votes)
8 May 2013 guy Cheshire cat
Shades of Inhibition - Optical Illusions with Lateral Inhibition

Look carefully at the optical illusion in figure 7. The green cylinder appears to cast a shadow across the checkerboard. However, the shades of the squares are not what they appear to be. Photoreceptors in the human retina are wired to the brain in such a way as to emphasize...

Average: 4 (2 votes)
8 May 2013 guy checker shadow illusion
Homemade Telegraph

Construction plans and suggestions for a homemade telegraph. Serves as a good application for studying electromagnets.

Average: 3.9 (16 votes)
12 Apr 2013 guy homemade telegraph
Hair, Balloons and Static Electricity

This lesson describes and explains the common effects of static electricity. It provides instructions for making a "pith ball" to study static electric effects from different materials, and includes data on many common materials.

Average: 3.8 (154 votes)
24 Mar 2013 guy sciphile and balloon
Balancing Magnetic Coins

This lesson describes a magic trick with magnetic coins (or washers) that demonstrates some important principles in magnetism. It's a good lead-in to a conversation on magnetic materials and magnetization.

For other ideas and more in-depth explorations of magnetism, che...

Average: 4.6 (5 votes)
3 Mar 2013 guy
Magnetic Materials

This lesson is a brief guide to exploring magnetic materials. It lists a variety of everyday metals, their magnetic properties, and where to find them. Students are encouraged to locate as many examples as they can, and test them with magnets. A checklist for students is atta...

Average: 3.5 (102 votes)
3 Mar 2013 guy
Diamagnetism - Levitating Graphite and Frogs

Diamagnetic materials are repelled by a magnet, in contrast to magnetic materials (like iron), which are attracted to a magnet. This lesson describes several demonstrations of diamagnetic repulsion using water and graphite (both diamagnets), with inexpensive setups. The most...

Average: 3.8 (6 votes)
17 Feb 2013 guy Pyrolitic graphite levitation
Faraday Motor

This lesson shows how to construct and operate a modern version of the first electric motor, invented by Michael Faraday. It serves as an excellent demonstration or hands-on activity to show the basic principles behind the operation of an electric motor.

Learning goals:...

Average: 4 (4 votes)
30 Jan 2013 guy Faraday motor
A Floating Compass

This lesson provides

  • plans for making a simple compass and
  • tips on magnetizing a needle

learning goals:

  • understand the mechanism behind magnetization
  • figure out which way is north

For other ideas and more in-depth...

Average: 3 (1 vote)
28 Jan 2013 guy
Minimalist Motors


Building a simple motor is much easier than most people realize. All it takes is a battery, a magnet and a piece of wire. This lesson reviews some simple motors and demonstrates a minimalist design constructed from a button cell battery, some wire, and a small but str...

Average: 5 (2 votes)
26 Jan 2013 guy
An Electric Screw Motor

This lesson gives instructions for one of the simplest and most popular designs for a homemade motor. It can be used as an in-class demonstration, or a hands-on activity for students, or a take-home kit. In any of these modes, it offers a wonderful introduction to the working...

Average: 4 (4 votes)
25 Jan 2013 guy screw motor
Iron and Magnets

This lesson provides general backround on magnets, and suggests several classroom activities involving magnets and iron filings. These include 

  • identifying magnetic materials
  • staging paper clip battles
  • finding the north pole of a magnet
  • maki...
Average: 3 (9 votes)
25 Jan 2013 guy bar magnet with field lines
Basic Electromagnets

This lesson provides some general background on electromagnets and describes three simple activities for students to explore on their own. For reference, it also includes formulas for the magnetic field strength around several common types of electromagnets.

learning go...

Average: 2.8 (4 votes)
25 Jan 2013 guy wire solenoid with bolt
Classroom Rail Gun

This lesson introduces two homemade versions of the "electric rail gun", a device that uses the principles of electromagnetic propulsion to drive a rod or axle along a pair of conducting rails. Both versions are suitable for in-class demonstration or hands-on activities. They...

Average: 4.2 (23 votes)
25 Jan 2013 guy rail gun with magnets
Safety Pin Motor

This lesson describes a simple motor that can be constructed in 15 minutes with inexpensive materials. It involves all the basic principles of motors involving magnetic force, electromagnets, and commutators (rotating switches common in many commercial motors). This device is...

Average: 3.2 (6 votes)
25 Jan 2013 guy safety pin motor
A Survey of Simple Electric Motors

This lesson provides general background on motors and surveys a number of projects for constructing simple motors.

Motors teach us about several of the basic ideas of electromagnetism, but the fundamental operation of a motor rests on only two simple principles:

Average: 3.5 (2 votes)
24 Jan 2013 guy


title description rating post date author
Getting to Mars the Easy Way

Two different methods of getting to Mars are proposed. A simple analysis shows that one is better than the other. The reasons for the difference are explored, yielding an insight into orbital mechanics. The topic is appropriate for any high school physics class familiar with...

Average: 4.5 (2 votes)
19 Aug 2014 gsgreenstein Mars from Hubble


title description entries post date author
Bernoulli Effects

A series of six lessons connected to Bernoulli's principle, which can occupy anything from one to several hours of class time. Don't pass up the smoke ring demos at the end, which make for a terrific finale.

6 22 May 2015 guy
Afterimages and Optical Illusions

A sequence of lessons involving effects of visual desensitization. Focuses on several optical illusions. Occupies 1 to 2 hours of class time.

4 5 May 2014 guy
Magnets and Materials

Up to two hour's worth of basic exploration in magnets and magnetic materials.

6 11 Apr 2013 guy
Lorentz force

The best experiment for demonstrating the Lorentz force: the electromagnetic force behind electric motors. Good for one class.

2 21 Mar 2013 guy
Magnets and Motors

A sequence of lessons on magnets and motors to cover 5 to 6 classes (each 30 to 60 minutes) in logical progression.

6 20 Mar 2013 guy