Our next meeting...
Click here for a map and directions. Parking will be free that night in the underground garage. There is a graduation that night as well. Early comers will probably have to pull a ticket but the gates will be up when they leave. The locations are the same as last times - Take one set of escalators from the Great Hall (where tickets are sold) up to the ground level of the Museum. Go past the Food Court and bathrooms to the green stairs and up half a flight. Ruth will have signs up.

Future Meetings
July 28-August 1	AAPT Summer Meeting, Greensboro, NC	http://www.aapt.org/

Click here for:   Job openings    

At our last meeting...

…at Northwestern University, we were welcomed by Art Schmidt with donuts, coffee, and a really nice phenomenon.  It was a piece of equipment made by C. J. Overbeck at Northwestern back in the 40s or 50s when he was in charge of introductory physics. There is a wheel with seven 5cm diameter lenses mounted in it.  The wheel had a belt that looked like it attached to a variable speed motor.  There was an arc lamp, a 2mm slit and a 70cm steel wire arranged so that the light from the lamp went through the slit, past the wire, and through one of the lenses. When the wire is plucked and the lenses spun at the proper speed the whole system projected a strobed image of the wire.  You could clearly see not only the fundamental mode but the high pitched wave patterns on the wire itself (transients?).  When a bow is used we were told those waves were sawtooth, but the bow was old and needed rosin.  Anyway I didn’t see sawtooth waves, but the ones I did see were really interesting.  We’ve all seen standing waves and their nodes.  This is the first time I’ve seen the disturbances in the antinodes.

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Bill Blunk (Joliet, retired) rushed us to another room where he had a 15cm diameter lens with a 2.3m focal length.  The lens was in the center of a poster board and the board covered the window.  Bill stood a couple meters back from the window with a 30cm square frosted pane of glass.  We observed the image from behind.  We saw a nice image that covered the sheet.  In color!!!  Unfortunately it was upside down.  Turning the lens over did not help.  Neither did turning the pane.  The lens was $25 from surplusshed.com – Catalog #LenL 3855D. (The URL in the print Reminder was incorrect.)

Bill also had a nice green laser he bought for $34.97 + 7.90 shipping.  Go to http://www.jasperlaser.com/index.php?/forms/basement. (This is also a correction from the print version. You must use this URL to get the lower price.) Phone 997-388-7362.  It looked like a good quality and uses two AAA batteries.  Bill says they are useful for pointing out items in the night sky as the beam is visible if you are standing near the pointer.

Earl Zwicker (IIT, retired) visited Rudy Keil and his wife and picked up a briefcase of assorted slide rules and drafting supplies from the 50s.  We all reminisced a while and then passed the case to a young man (whose name I missed) sitting next to me.  He promised to bring it back in another 50 years.

Gordon Ramsey (Loyola University) described the math that could be used to describe the equilibrium position of the leaf of an electroscope.  We decided that if you use the equations to program a computer, you could use different charge configurations and find one that produces an energy minimum.  That would answer our question from last month of what the charge distribution on an electroscope is.  Everyone I talked to last month thought the distribution is probably not uniform even though we all draw it as if it were.   Gordon passed out a sheet with all the math.

Stewart Brekke (CPS, retired) brought some wooden slats that looked to be about 50cm x 4cm x 0.3cm.  He placed a slat on the table with 10 or 15cm overhanging the edge.  Then he placed a newspaper over the slat.  He gave the end of the slat a judo chop and sure enough the slat ripped right through the paper and flew into the audience unbroken.  More than once I’ve stood in front of my class with a piece of equipment that refused to work the way it did when I practiced it before class.  We all gave suggestions to Stewart such as more paper or flatter paper.  He finally got the stick to break to the applause of the entire group.

Ann Brandon (Joliet West High School, retired) brought a couple toys she got shopping in  Branson.  There was an inchworm that inched and a ladybug that circled and flipped.  The company was Schylling in Rawling, MA 01969.  Ann suggested a writing assignment to describe the motion.  I thought it was a good idea.

Paul Dolan (Northeastern Illinois University) brought a small picture frame (15cm square) and put it on the overhead.  He put a half dozen marbles in the frame and shook them back and forth.  He then said the marbles could be used to describe the ideal gas laws. Paul said the law involved Pressure, Volume, Temperature, and the number of particles.  The Pressure is the marbles hitting the sides of the box.  The Volume is the area of the box open to the marbles.  The temperature is the average kinetic energy of the marbles, and of course the number of marbles corresponds to the number of particles in a gas. Then Paul shook the marbles and we listened to the collisions with the sides of the box (pressure) as he added or subtracted marbles (n), as he shook hard of soft (T), and as he confined the marbles to a smaller part of the box with a wall.  Paul suggested you put a transparency sheet on the overhead so you don’t scratch it with the picture frame as you shake it around.

Tom Senior (New Trier High School) brought a board with a series of pendulums on it.  The bobs were made of wooden “beads” about 3cm in diameter.  Each bead was drilled through the center and hung with two strings.  The lengths of the strings were adjusted on screw clamps so that the longest made 16 swings in 10 seconds, the next made 17 swings in 10 seconds, etc. through the 10 pendulums.  When he used a board to pull back and release all the pendulums together, they formed a nice sin wave.  The pattern became chaotic and a short time later each pendulum was 180o out of phase with the next pendulum.  Chaos returned and a short time later the pendulums formed a sin wave and finally all swung in phase.  The whole process took 10 seconds. Tom told us the pendulums were part of a workshop he did so all the teachers at the workshop made one probably in under an hour.  It’s one of those things like Newton’s Cradle.  You can’t stop watching it.  You can buy one for $75 from Cenco.

Sudarsan Kowligy (Carver Military Academy) reported an experiment done at his high school.  Beans were grown under three fluorescent lights, one red, one white, and one blue.  The blue light grew the tallest plants and the red light worked poorly.  The question was how to explain this. There were lots of suggestions for further measurements of the spectrum of each of the lights, and the power of each light as registered by a light meter.

Roy Coleman (Morgan Park High School, retired) led a brief discussion of the coefficient of friction between a car and the road necessary for the car to do various things.

Gordon Ramsey (Loyola University) put an illusion he got from a website called damncuteillusion.  It consisted of a circle of magenta dots that flashed off and on in sequence.  The off spot would leak green and would circle as the magenta spots went off.  It’s fun because you know there is no green spot.

<>Art Schmidt (Northwestern University) ended the meeting with a discussion of lenticular images.  Those are the things you get that have one picture when you look at it in one direction and another when you look from a different angle. 

There are really two different pictures under the lens which is a series of convex lines.  The light from each picture is bent in a different direction by each lens.  Art’s son wrote a JAVA program so that two pictures could be fused for a lens.  Art passed out the program, a clear lens, and a few pictures for each of us. Art warned that you need a good printer that won’t smooth out the pictures and blend them.  Also you need a certain size, 60 lines/inch so you can’t copy them on the usual copier as it changes the size slightly.

Maybe it’s just me but it seems to me the meetings have been more and more fun lately.  I’ve noticed that the June meeting attracts people who weren’t able to come during the rest of the year.  Hope to see you there!

Reported by Pete Insley.

For any information regarding ISPP contact Gerry Lietz at DePaul University, Physics Department, 2219 N. Kenmore Chi. IL 60614 phone: 773-325-7333 e-mail glietz@depaul.edu. ISPP home page:  http://condor.depaul.edu/~glietz/ispp/ispp.html

Sabbatical Leave Replacement:
The Department of Physics at Dominican University, River Forest, IL, invites applications for a sabbatical leave replacement for the Spring Semester of 2008. Job duties would involve teaching the lecture of a 2nd semester algebra-based general physics course which meets 3 times per week and has 2 accompanying lab sections each week. Desired qualifications are a master's degree or ABD standing; a doctorate is preferred.
Please contact: Dr. Gerald Gulley   ggulley@dom.edu  (708) 524-6911

St. Martin de Porres High School, Waukegan, IL
There is an opening in ’07-’08 for a qualified person to teach three sections of Physics, to Juniors and Seniors. This course has not been taught at St. Martin de Porres High School previously, so we will look for someone who can design and start this program. The position will also involve teaching computer courses. Each teacher also serves as advisor to a group of students (one level or another) helping them with organization, community-building, academic strategies for success, monitoring of academic progress, etc.  (Also, a program in process of development). Resumes and letters of interest may be sent to my attention electronically or by mail.
Judy Murphy, OSB, Principal, St. Martin de Porres High School, 515 S. Martin Luther King Avenue, Waukegan, IL  60085
jmurphy@smdpwaukegan.org

Walter Payton College Prep, Chicago, IL
We are eager to find a qualified teacher of AP Physics C to teach the mechanics curriculum from late August 2007 to late January 2008.  The class typically meets three days a week for 1.5 hours on Mondays and Fridays, and 3 hours and 20 minutes on Wednesdays, which offers wonderful opportunities for labs and extended problem solving.  I would gladly provide my curriculum materials and would also welcome the individual approaches of the substituting teacher.  Given the caliber of the students and the extended class periods, this teaching assignment is a rigorous one and will demand the skills of someone who does not rely on lecture or teacher-centered demonstrations to convey information. I can sincerely say that this class will be a real treat for whoever accepts the challenge.
Sam Dyson, Walter Payton College Prep, 1034 N. Wells St., Chicago, IL  60610
ph. 773-534-0034 ext. 24993, fax 773-534-0035    dysons@wpcp.org    www.wpcp.org

Harold Washington College (contact MDavis@ccc.edu)

Joliet Central High School (www.jths.org)

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