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Thank you for joining us in Atlanta for the Physics Demo Show. We hope you enjoyed the demonstrations and ideas as much as we enjoyed sharing them with you. It was a great time and hopefully you will have found at least one idea that you'll be able to use in your classroom. Congratulations to Paul Becht of Bishop Moore High School in Orlando, Florida who won the drawing for a free Rotating Stool! Hopefully your students will enjoy it as much as we did.
As promised, here is a description of each
demonstration done in the workshop. Use the menu on the lower left to jump to
your favorite demo. We hope to see you again soon at a state or regional
conference, or next year in Dallas! |
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Neon Lasso
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Neon Lasso |
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Attach a small neon nightlight to the end of an extension cord. In a dark room, twirl the neon light around in a circle. (Caution: Make certain that the area around you is clear.)
What do you observe? Why
do you see multiple images of the light? What produces the dark spaces
between the images? If the light was continuously lit, observers would see a circle because of persistence of vision. The neon light cycles on and off at 60 cycles per second (like AC electricity), so observers see a dashed circle.
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Focus a 35 mm slide of
your choice on a sheet of white paper. After obtaining a sharp image,
remove the paper. Now rapidly swing a dowel rod up and down in the area
previously occupied by the paper. What do you see? Why does the entire
image seem to appear in midair? Reduce the rate of swinging until the
entire image is no longer visible at one time? Why does reducing the
frequency of swings cause this to happen? Now increase the rate of
swinging to the point where the entire image just begins to appear.
Measuring the time per one up or down swing cycle will give you a rough
estimate of how long the image persists in your eye-brain system. ( The
rate of disappearance is directly related to the time of one swipe of the
dowel.)
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Demonstrating Additive Color Mixing with Chemical Light Sticks
Chris Chiaverina
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This apparatus consists of a sphere that represents a raindrop, along with three colored dowels. One dowel is white, representing a ray of sunlight. Another is red, representing a ray of red light, and another blue for a ray of blue light. The angles between the dowels show the angles between incoming sunlight and outgoing refracted and internally reflected red and blue rays of light. A volunteer crouching in front of your chalkboard shows the class how the only drops that cast light to him or her originate in drops along a bow-shaped region. Hence the geometry of the rainbow’s bow shape. Paul G. Hewitt
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Click here for Details on the Color Addition Spotlights
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Demonstrate the basics of color addition easily with a set of three spotlights. Just aim the spotlights at a white screen and ask students to predict the combinations. When you have white light, hold up your hand and make shadows!
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This demo was inspired by Gorazd Planinsic’s recent article in The Physics Teacher, “Color Mixer for Every Student” [TPT 42, 138-142 (March 2004)]. Insert a Red-Green-Blue Flasher LED into a normal ping pong ball. The LED will project small circles of light onto the front surface of the ball, and the rest of the ball will show the resultant color when two or more colors are lit. From the Exploratorium's "Try This" Web Cast Click here to see Paul Doherty and Gorazd Planinsic's demo of the RGB Ping Pong Ball Chris Chiaverina |
Click here to get the complete article from The Physics Teacher magazine
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The long plastic bag demo nicely illustrates Bernoulli’s principle. If you were to blow it up by placing it firmly to your mouth, many lung-fulls of air would be needed. But when you hold it in front of your mouth and blow, air pressure in the stream you produce is reduced, entrapping surrounding air to join in filling up the bag. So you can blow it up with a single breath! This is especially effective after your students have counted many of their own breaths in attempting to fill up the bag! Paul G. Hewitt Click here for details on the Bernoulli Bags
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Toss the rubber mat onto a smooth flat surface, such as a lab stool. Pick it up with your right hand easily (as long as you pick it up from the edge). Try to pick it up with your left hand, and it sticks to the stool, lifting the stool up too (as long as you lift from the hook in the center). This dramatic demonstration shows the power of atmospheric pressure! As the middle is raised, a low-pressure region is formed because air cannot get in. The rubber sheet behaves as a suction cup, and the entire stool is lifted when the handle is raised. Paul G. Hewitt
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Another Cool Atmospheric Demo...
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You've probably seen comparisons of the gravity on different planets. How about a comparison of atmospheric pressure? To simulate the atmospheric pressure on earth, cut a 1.3m length of 1-in-square iron bar. The bar weighs 14.7 pounds. Rest it on your hand to show the force earth's atmosphere exerts on each square inch of you. Mars's atmospheric pressure, in comparison, can be shown with an iron bar only 1.3cm tall. Venus's would be 1300m tall! How would these differences affect spacecraft and humans visiting those planets? The bars of iron for this demo may be obtained at your local metal shop. Thanks to Paul Doherty of the Exploratorium for this idea. Paul G. Hewitt |
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 Chris & Paul battle it out in Atlanta
Click here for details on the Air Cannon
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Use the Air Cannon to create your own “Air Duel.” Pull back on the handle and release a harmless ring of air that quickly travels up to 30 feet! If you practice, your aim will be better than ours was! Chris Chiaverina & Paul G. Hewitt |
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Chiaverina sets record with over a hundred Attendees creating a human circuit!
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This very cool device consists of a 1.5-inch ball with two small metal electrodes. When the two electrodes are touched simultaneously, the ball flashes and makes a strange tone. The Energy Ball utilizes a field effect transistor so even the slightest conduction between the two electrodes activates the Sphere. The Energy Ball is completely self-contained and requires no additional batteries or energy source. It is often used to demonstrate closed and open circuits, just line up your students in different "circuits" and complete the connection. Chris Chiaverina
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 Click here for details on Energy Balls
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Teachers catch the wave in Atlanta!
Click here for details on Standing Wave Kits
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The Simple Standing Wave demonstration consists of a battery holder, motor with offset weight, spinner, and elastic string. I. Demonstrating Standing Waves · Activate motor unit. · Hang the motor from a string. Adjust length of string until a standing wave is obtained. To change number of anti-nodes in standing wave pattern, simply vary the length of the string. · Try changing the motor frequency by adding weight to the wooden oscillator, such as a wood screw. II. Determining Wave Speed - Method I · Establish standing wave on the string. · Measure the distance between adjacent nodes. Multiply this distance by two to obtain wavelength of disturbance. · Use a strobe light to measure frequency of wave. · Calculate wave speed from v=f·λ III. Determining Wave Speed - Method II · Use balance to find mass of motor unit and mass of a string sample. · Calculate weight of motor unit in newtons. This equals tension in string. · Find linear density of string (µ= mass/length). · Calculate wave speed from v= √T/µ. Chris Chiaverina |
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Measuring the Wavelength of Light with a Common Ruler
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Measure the wavelength of laser light in class with a common ruler and the familiar formula, ml = d sin q. The raised millimeter ridges of a plastic ruler make up your diffraction grating. How is this possible—with d being the 1-millimeter distance between ridges, very large for a diffraction grating?
The answer is to use grazing light and a long distance from the ruler to the viewing screen. When the laser is angled 1:10 (5.7_) as shown in Figure 1, d as seen by the laser beam is “compressed”—less than 1 mm—sufficient for viewing diffraction fringes centimeters apart when the screen is several meters away. Paul G. Hewitt
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Click here for details on Happy Sad Balls Paul G. Hewitt
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1000 Bounces Guaranteed Can a rubber ball wear out? It can with a little slight of hand. Trade the “happy” ball in this pair for the “unhappy” ball, and show students a completely inelastic collision. Easy to use and endlessly intriguing, our Happy/Unhappy Balls are great for teaching discrepant event science, polymerization and the coefficients of friction and restitution. Each set comes complete with two balls, information on their physical and chemical properties, plus a ton of fascinating experiments for you and your students to try. |
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The Bouncing Dart has one elastic end and one inelastic end. Investigate the momentum changes with both types of collisions by swinging the dart into a dynamics cart or standing board. Which collision, elastic or inelastic, will knock the board down or make the cart roll farther? Look at this demonstration in terms of force or momentum, and you’ll see that the elastic collision causes the bigger change. Paul G. Hewitt
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Paul G. Hewitt
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Try an ice-skater style spin on a Rotating Stool. Hold your hands out, then bring them in and spin faster, without touching the floor or wall! Did your angular momentum increase? No. Did your angular speed increase? Yes! What happened to your rotational inertia? It decreased. |
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The Doppler effect occurs when an observer hears a sound from a moving source. If the sound source is moving toward the observer, the perceived frequency will be higher than the actual sound frequency. If the source is moving away from the observer, the perceived frequency will be lower.
Setup instructions Chris Chiaverina Click here for details on the Doppler Ball
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Click here for details on the Groan Tubes
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Groan Tubes are interesting for demonstrations of sound, but they can also be used to teach about free fall. Turn the tube so it starts to “groan,” and quickly toss it to a friend (so that the tube stays vertical). Listen. The “groan” stops when the tube is in the air and resumes when it is caught! Chris Chiaverina |
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 Click here for details on Audioscope
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Audioscope will strike the right note in your classroom when you turn it on for an in-depth look at waveforms, harmonics, and the perception of sound. You can experiment with a variety of sounds and analyze the waveforms using three different high-resolution displays: real-time sonogram, spectrogram, and waveform graphical display. You can experiment with sounds from your computer's microphone, the included samples, or a recorded sound.
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Using Audioscope to Analyze Sound
To Do and Notice:
Some Questions on Waveforms and Spectra
Chris Chiaverina |
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Try this quick and memorable demonstration of radioactive decay and half life. Ask your class to stand. Each student flips a coin. If their flip matches yours, they remain standing. If it does not match, they clap their hands and sit down. How many half lives will it take for the whole class to decay?
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© 2004 Arbor Scientific
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