Sandra Broomes [Sherman School]
She distributed a hand-out concerning a problem involving sewers, which probably happens to some unfortunate person, somewhere, every day.
Arlyn VanEk [Iliana Christian HS]
[A problem in Hewitt's textbook Conceptual Physics:] A dish with water in it is set spinning, and there is a family of floating ducks on the dish. Since the water at the center of the dish is lower than at the sides, where will the ducks float? This problem was solved empirically, by setting the dish on an OLD! Phonograph. Ann Brandon [Joliet West HS] explained that the weight and the buoyant force must add to produce a net force into the center of the circle along the path of rotation of the ducks, who are still in the water as it rotates with the turntable.
Fred Schaal [Lane Tech HS]
He recently noticed that a very bright star [brighter than Venus, even], appeared to be in the same position several times when he looked for it. He concluded that the star could not have been an airplane, because it did not appear to move in the sky. It was suggested that he might have been seeing different airplanes in a landing pattern, where they are a minute or so apart on the same flight path.
Ann Brandon [Joliet West HS]
She passed out a sheet of graph paper [old chart recorder paper, actually], and asked peple to estimate the cross-sectional area of one shoe, in square inches. The people then weighed themselves [pounds], and calculated the pressure [standing on one foot and two feet] in pounds per square inch [lb/in2]. Most people obtained a number between 3 and 4 lb/in2 and it did not seem that the bigger people always had the higher numbers, since their feet were usually longer and wider also. The highest pressures are generated by people [primarily women] wearing "spike heels".
John Bozovsky [Bowen HS]
He showed a Stargazing cartoon featuring a box with pin hole, for safe viewing of the image of the sun during an eclipse. The observer would have to be a pinhead [zero cranial cross-section] in order to see the image, since otherwise his head would have blocked out the sunlight! Porter commented that, until quite recently, the sun's cornea [solar atmosphere] was visible only during solar eclipses. The eclipse in Madagascar in 1919 was used to confirm Albert Einstein's General Theory of Relativity, which predicted that light would be deflected by gravity when it passed close to the sun, so that stars seen during an eclipse would appear to be in the wrong places. The dating of total eclipses of the sun is an important piece of information for cosmological considerations. The Arabs after 700 AD kept very good records of total eclipses, and clearly described them as such.
Of course, Europe was still in the dark ages at this point, and there were no serious European astronomers until the time of Copernicus. In fact, many of the bright stars still have their original Arabic names.
John also gave away gallon cans [without tops] that can be caused to collapse because of air pressure when the air inside is removed.
Bill Shanks [Joliet Central HS, retired]
Demonstration of the Bernoulli effect: Let a meter stick extend over the end of the desk, blow between two soda cans, and they will come together.
can can ------------|---------------------- quick demo | | air | | Desk |blowing | down
Al Tobecksen [Richards Vocational HS]
He proposed a game based upon removing objects from rows, with the rows initially containing 1, 3, 5, 7 objects. Two people take turns removing some or all objects from only one of the rows, and the person who makes the last move loses the game. To stimulate student interest and excitement concerning his potential humiliation, he promised an A for the grading period to any student that beat him in the game. What is the winning strategy? [more about this in the future!]
Bill Colson [Morgan Park HS]
He brought in several objects that he purchased recently at a gift shop at Navy Pier. One was a half-black, half-white object, that appears to show colors when it is spun. Also, there is a spiral that gives the impression of up-down movement after you look at it for a while.
He also passed several spinning patterns reprinted from Turntable Illusions: Kinetic Optical Illusions for Your Record Turntable, by John Kremer, which is available from Horizons Publishing Company; Box 205; Fairfield Iowa 52556 for $12.95.