Mathematics-Physics High School Meeting
28 September 1999
Notes prepared by Earl Zwicker

John Bozovsky (Bowen HS)

told us that the Principal's Scholars Program, which has Saturday morning sessions for students at UIC, Oct - Dec, is looking for an instructor for Amusement Park Physics. Call 312-575-7860 to find out more.

Ann Brandon (Joliet West HS)

set up an experiment to detect differences in air resistance for 2 objects of equal mass. The objects were solid wood blocks, each suspended - in turn - as a bifilar pendulum of the same length (about 1.2 meters). Ann handed out stopwatches to some of us (available at K-Mart), and we observed (and Ann wrote on the board for all to see) the time (in seconds) for 5 swings of wood block 1. This was done both for large amplitude (about 15 deg) and small amplitude swings.

This was repeated for wood block 2, which had a different shape and which presented a different area (than wood block 1) normal to its motion through the air. Intuitively, one might expect the block with greater area to encounter greater air resistance to its motion, which might produce a difference in swing times. Upon looking at the data for both blocks, we concluded that there is no significant difference, and therefore air resistance is not a significant factor in their motion. However, there was an obvious difference in times between large and small amplitude swings for each block. Why? Any ideas? Thanks, Ann!

Bill Blunk (Joliet Central HS)

showed us an effective way to use paradigms to teach physics. As an example, using the distance (d) an object travels in free fall under gravitational acceleration (g) for a time (t), we know that d = gt2/2. Let's suppose that g = 10, t = 2 and d = 20. Bill challenges his students: If you can give me the proper units for g, t and d, I'll give you a ten! When a student gets a correct answer, he gives them ten cents! Neat!

Sue Sitton, Associate Dean of Armour College, IIT

introduced us to two IIT Camras Scholars, Mitch Mabrey and Pat Wagstrom. They told us they are working on a program to visit local schools, both high school and elementary, in order to give students information on careers in engineering. They are looking for ideas from us to make things interesting to those students during their visits. Any ideas? Want more info? Please contact Sue at 312-567-6781.

Bill Shanks (Joliet Central HS, ret)

showed us some interesting physics using a Solar Radio (available at Sam's Club, \$69). An array of solar cells on top of the radio converts incident light (electromagnetic energy) into electrical energy to power the radio, which vibrates its speaker cone (mechanical energy) producing sound waves (acoustical wave energy). As the angle of incidence of the light from the source is changed (by tilting the radio, for instance), the amount of light on each unit of area of the array is decreased, decreasing the available energy, so that the sound output of the radio will decrease toward zero. Bill then made 55 turns of a crank on the radio, winding up a spring (mechanical potential energy). As the radio was played, we could see the crank slowly turn as the spring unwound and the mechanical energy was converted (with a built-in generator) into electrical energy to power the radio. Turning up the volume of sound caused the energy to be used more quickly, and the crank turned faster! What a pretty example of the interplay beween different kinds of energy! Beautiful, Bill!

Bill also had three mirrors set up orthogonally as a "corner mirror," which reflects any beam of light hitting them directly back at the source. How does it work? Can anyone explain?

Fred Schaal (Lane Tech)

pointed out that we could get a good view of the planet Venus, rising in the early morning eastern sky, just before sunrise. Especially nice with the near-full moon during the next weeks.

Fred drew our attention to inequalities. For example, for a straight line y = mx + b, we might have y = (1/2)x + 2. On a graph of y vs x, below the line y < (1/2)x + 2, and above the line y > (1/2) x + 2. Our hand-held calculators seem not to enable us to display a band of (x,y) pairs that lie between a minimum and maximum set of values. Is there any way to do such a thing on any hand-held calculator? Interesting question!