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LAST MEETING OF THE SCHOOL YEAR
 
 

June 4

(Tuesday)

Museum of Science and Industry -- Ruth Goehmann

ANNOUNCEMENTS…

…Physics Day at Great America is May 7 and 8.  They need help.  Contact Ann Brandon, llbrandon@aol.com.

…the John Rush Award will be given at the June 4 Museum meeting. The award is in memory of John Rush, who used phenomena which students hadn't experienced, to aid in inspiring them in physics. The award is given to one of our members who has made mind-catching and useful contributions to the group. Past recipients have been:
 

1983	Jim Williams	1984	Chris Chiaverina	1985	Earl Zwicker
1986	John Milton	1987	Gerry Lietz	1988	Steve Luzader
1989	Bill Blunk	1990	Larry Alofs	1991	Art Schmidt
1992	Tom Senior	1993	Jim Szeszol	1994	Ann Brandon
1995	Roy Coleman	1996	Pete Insley	1997	Bill Conway
1998	Bill Shanks	1999	Paul Dolan	2000	Nick Drozdoff
2001	Bailey Donnally

The committee this year is Bill Blunk, Paul Dolan, Nick Drozdoff and Bailey Donnally. Send them your nominations!

AT OUR LAST MEETING…

…We were welcomed to Lake Forest College by Mike Kash and his physics department colleagues, Harold Schnyders, Scott Scharpe, Bailey Donnally and Bill Conway.

After some announcements, Harold Schnyders showed us an array of "super bright" LEDs arranged to spell out "LFC." We were given diffraction gratings and when we looked at the LEDs we saw the entire visible spectrum! Harold provided some technical information and told us that a monochrometer analysis of the spectrum showed a peak at about 450 nm. The device is a blue LED whose light is absorbed by white phosphors, as in a fluorescent lamp, and reradiated across the spectrum. Peak current is 20 mA. A 2.5 V supply with a 100 W dropping resistor, or  9 V, 330 W, was suggested. The giveaway, was then passed out - a superbright LED for each of us!

Scott Scharpe set up an aluminum tube (Pasco) and dropped an aluminum slug through it, followed by a magnet. We expected, and saw, that the magnet took some time (about 4.5 s) to drop through the tube. Then Scott set up another tube that had a vertical cut along its entire length. We were each given a remote unit and were asked to predict by making a selection on the remote the time it would take for a magnet to fall through this tube. We were using Lake Forest's new Personal Response System that is used with their students to enhance class participation. We were able to see the question on the screen and after we had voted saw a histogram of our predictions. The time of fall was about 3.5 seconds. We could not fully explain this in terms of eddy currents around the circumference of the tube. (This was brought up at a meeting a few years ago. Any ideas? Bring them to Northwestern.)

Earl Zwicker (IIT) brought out a "popper" that we had seen earlier this year at New Trier High School. He proceeded to provide us with a lucid explanation of the forces involved in each of the four cases he demonstrated, with the flexed popper initially up and down on the table top and on a beaker. And of course he involved us in the discussion of the phenomenon.

Bill Blunk (Joliet Central High School) showed us a counterintuitive phenomenon dating back to meetings at Lake Forest several years ago, first shown by Ed McNeil. Bill had used a ceramic tile drill to make a 1/4" hole in the bottom of a small bottle. He put his finger over the hole and filled the bottle with water. When he removed his finger the water did not run out of the bottle until he pierced the surface tension film with a nail. Then Bill filled a Pepsi bottle and covered the top with waxed paper, then turned the bottle over, peeled away the waxed paper, and the water remained in the bottle until he inserted a nail (well… not on the first try…).  Then he did the same thing with an even larger diameter bottle! Surface tension seemed to be ruled out. Finally Bill explained that hidden under the waxed paper was circle of acetate material (overhead transparency) that was covering the opening. The nail pushed the acetate cover out of the way!
 

Earl's pepper

Bill's bottle

Ann's straw

Charles Mattes….. passed around a National Geographic gift catalog and noted especially the physics related items, such as a Galileo thermometer, an orery, and a number of holography products. Then he told us of an experience he'd had in Pleasant Prairie, WI, a couple of years ago. He saw as he looked across a lake what looked like an "uneven" horizon and with binoculars thought he saw the tops of trees in Michigan, some 85 miles away. It turned out to be a mirage, a reflection by the atmosphere of the opposite shore of the lake. Harold Schnyders said this is called an "arctic" mirage and requires a large temperature gradient between cold water and warm air.

Ann Brandon (Joliet West High School) showed us a "sinking of straws" exercise she does with her students to get them thinking about forces and buoyancy.  She seals the bottoms of soda straws with clay or uses a low temperature hot glue gun ($4 from Michaels). The straws are placed in water and float at a certain level. The students are asked to predict how many BBs (from Wal-Mart) can be put in a straw before it will sink four more centimeters. Our guesses ranged from one to ten.  We saw that four were needed.
 

Bill Conway had two empty half gallon orange juice cartons and showed us how to use them to illustrate air pressure. He put them on the floor, capped, and asked someone to stand on them. Joe Hermanek (NEIU) volunteered. The cartons flattened a little but supported Joe. Bill uncapped the cartons and when Joe stepped on them the air was forced out and they flattened completely. The Bill blew into the cartons to reinflate them and capped them. Once again they supported Joe's weight. Bill showed us some toys from Burger King that connected in "Rube Goldberg" fashion and could illustrate a sequence of energy conversions.

Tom Senior (New trier High School) demonstrated a version of the familiar speed of sound experiment using resonance in a tube. Plastic tubes used to protect fluorescent bulbs come in 8 foot lengths at home supply stores and can be cut to shorter lengths. One end is capped with a PVC end cap and the tube filled with water. A smaller diameter tube inserted into the larger tube can be moved up and down to change the length of the sound path. Instead of a tuning fork a piezo buzzer connected to a 9 V battery is used as a sound source. Small diameter plastic tubing goes from the buzzer to the top of the tube; this attenuates the sound. Resonance lengths can then be found. Tom modified this familiar experiment to eliminate the water. He found that a cap from a water bottle fits nicely inside the tube.

He put the cap at the end of a wooden rod and moved it along the length of the tube to locate the positions of the resonances, one half wavelength apart. He used a Radio Shack dB meter to find the frequency of the buzzer. The output of the dB meter to a $39 DVM that has a frequency scale. The buzzer frequency is about 3.51 kHz. Tom gave us a handout of the old "wet" version.

Submitted by John Milton

Art Schmidt	Jan Dudzik	Earl Zwicker
Bailey Donnally	Bill Conway	Mike Kash
Ann Brandon	Paul Dolan	Ruth Goehmann
Tom Senior	David White	David White
Kate Cleary/Van Bistrow	Chris Chiaverina	Gerry Lietz
Earl Swallow	Roy Coleman	Kevin McCarron

.............................................................................................................................
During 2001-2002

Coordinators:	Paul Dolan
	Gerry Lietz
	Earl Zwicker

ISPP Authors:	Gerry Lietz	Data Base Managers:	Roy Coleman
	Art Schmidt		Earl Zwicker
	John Milton
	Pete Insley

Photographers	Paul Dolan	Treasurers:	Ann Brandon
	Art Schmidt		Pete Insley
	Gerry Lietz
	John Milton
	Earl Zwicker

Special Events Committees:
     Physics Day - Ann Brandon, Roy Coleman (Co-Chairs)
     John Rush Award - Bill Conway (Chair), Bill Shanks, Paul Dolan, Bill Blunk (ex-officio)
     Harald Jensen Award - Brian Wegley (Chair), Keith Bellof, Martha Lietz, Ann Brandon
     Annual Tri-Physics Meeting - Bruce Illingworth, Walt Schearer, Gerry Lietz
     National Bridge Building Committee - Carlo Segre
     New Member Committee – Kevin McCarron (coordinator), Ann Brandon, Pete Insley, John Milton

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