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ISPP REMINDER

December, 2006

OUR NEXT MEETING...

                                                              ...is at De Paul University
                                                                         Tuesday
                                                                         December 5, 2006
                                                                         6:30 - 9:00 PM

Click here for directions and a map.

FUTURE MEETINGS...

Jan 17 (Wed)	Elmhurst College	Earl Swallow
Feb 13 (Tue)	Northeastern Illinois University	Paul Dolan/Joe Hermanek
Mar 7 (Wed)	Chicago State University	Mel Sabella
Apr 3 (Tue)	Lake Forest College	Mike Kash/Bailey Donnally
May 7 (Mon)	Northwestern University	Art Schmidt
June 5 or 12 (tentative)	Columbia College or Museum of Science and Industry

BRIDGE CONTEST NEWS

Chicago Region Contest is at IIT, Thursday, February 15, 2007.

High School Bridge Building kits are now available from the IIT admissions office for $4.00 each (check or money order - no cash). If you e-mail Roy (rcoleman@iit.edu) by December 2 with how many you need, he will bring them to the DePaul ISPP meeting.

AT OUR LAST MEETING . . .

We were greeted at Oak Park and River Forest High School by Kevin McCarron, and two new teachers were introduced. Norman Hodgson and Rich DeThorne (who will start student teaching in a couple of weeks). They received New Teacher Bags.

We were greeted at Oak Park and River Forest High School by Kevin McCarron, and two new teachers were introduced. Norman Hodgson and Rich DeThorne (who will start student teaching in a couple of weeks). t the end of the meeting they received New Teacher Bags from Debby Lojkutz.

Kevin started out the meeting with his Play-Doh. He rubbed out a couple cylinders and attached them to 3V and a milliammeter. The longer roll measured 4ma and the shorter roll 7ma. Then he made a short fat roll that pinned the meter at 10mA. Kevin is using Play-Doh to investigate the effects of length and area on resistance. John Milton (DePaul University) suggested that various colors of Play Doh have different resistances. Bill Blunk (Joliet Central, retired) suggested that this is where the resistor color codes come from. Kevin had a small tub of Play Doh for each of us to take home and try.

Jamie Chichester (Oak Park and River Forest High School) had a matchbox car and track set up with a loop. He had a pair of photogates at the end of the track about 20cm apart to time the car going through and calculate the speed of the car at the end of the track. He attached an index card to the car to trigger the photogates. Jamie asks his students to calculate the PE of the car at the top of the track and predict its KE at the bottom of the track. His students use conservation of energy assuming no losses to friction. Then they run the car through the loop and the photogates, calculate its final velocity and KE and are surprised by a 30% loss on the track. The loss is mostly in the loop. The students discuss why the energy loss should be so much greater there. Someone made the suggestion to calculate the height that would allow the cart to just make it around the loop. Art Schmidt (Northwestern University) mentioned that at the top of the loop the normal force is zero for this case. He suggested it would make for an interesting roller coaster ride if this section of the track were missing. That of course led to various stories of roller coaster failures.

Paul Dolan (Northeastern Illinois University) brought some electric massagers that he got at Walgreens (I think). When he put them on the table they tended to rotate counterclockwise. He asked what would happen if he put it on a lazy susan. Sure enough, the lazy susan turned clockwise. He put a pad on the lazy susan to increase the friction, thinking the lazy susan would rotate faster. It did in one case, but in the other case the massager reversed direction and began to spin clockwise. I thought that was interesting but we did not pursue it. Paul got out a little (10cm high) pyramid with light strings on the top (about 7cm long) that lit and rotated. He expected the same effect but got only a small one. We decided that was because the device was already spinning when placed on the lazy susan. It needed a change in velocity to impart momentum to the lazy susan.

Art Schmidt (Northwestern University) followed up with a helicopter he got for $40 from geeks online. We think the email is xtremegeeks.com but we got variations on that. (I also saw it in Scientifics for $70.) In any case, this remote-controlled helicopter has two main propellers that spin in opposite directions and a small tail prop that gives lift.

This little thing is tricky. It flies but it’s very easy to crash it. The body tends to rotate in the opposite direction of the props, which operate independently of each other. The little prop on the tail lifts the tail so the big props propel the helicopter forward. However, tilting the body causes torques on the big blades that cause them to precess or tilt sideways. They can contact each other if the tail lifts too quickly. You can see a lot of rotational physics by playing with this thing slowly and carefully. It also gives you a good feeling for the dynamics of helicopter flying.

Max Lee (Joliet Junior College) brought various optical illusions sent to him in Power Point. One I particularly liked because it was new to me was a circle of red dots. The computer would turn off and then on one dot at a time around the circle. You’d think you would see a circle of red dots with one missing. What you saw was a green dot circling around. Max had other illusions that illustrated the way a color receptor in the eye can tire, but I liked this one best. (Max does not have a URL, but you can click here to get the Power Point file.)

Eileen Wild (CPS, retired) got out her trusty overhead projector and put on a transparency that said the equation that the flight of a butterfly is PR = S²/A.
R is the Reynolds number and A the area. I think P is pressure and S the speed of the wing but I’m not sure. We didn’t discuss it.

Eileen also balanced a saltshaker in a little pile of salt. When you blow the salt away the saltshaker is supposed to stay balanced. I guess you need to do it more slowly and carefully than we did. Everyone agreed the few grains left after blowing provided enough of a base to balance the saltshaker.

Rich DeCoster (Niles West High School) held up some Polaroid filters in front of the projector we were using to display the laptop computers on the front screen. Turning the Polaroid, he produced green and magenta on the screen. If you use the colors and make green circles with magenta triangles for “eyes” you can make the circle wink if you hold the Polaroid between the projector and the screen where the eye is.

Aaron Podolner (Oak Park and River Forest High School) videotaped a dancer doing a leap to show her center of mass moved in a parabola even though it looked like she simply floated. Aaron pointed out the movement of her stomach during the leap and then pointed out the movement of her head. He was looking for the parabolic motion that must be the motion of her center of mass. You can look at assorted videos at apodolner@oprfhs.org.

Carl Spight (Oak Park and River Forest High School) brought a thumb piano or kalimba that he played for us. It has a wooden body about the size of a large grapefruit and eight metal tines that are tuned to the white keys of a piano. These tines are fixed at the base and vibrated with the thumb. Their lengths vary to give different pitches with the octave having a length ratio of 2^1/2 instead of 2, as there would be with strings fixed at both ends.

Carl was also interested in “magnetic fluids” but no one had any information for him.

Finally, Kevin McCarron sent us back to the back row of the room where we could make some Tom Senior stadium horns and pick up some Play Doh resistors.

Thanks OPRFHS teachers for a very nice meeting! See you December 5 at DePaul University.

Submitted 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

BRING FRIENDS BRING IDEAS ! ! SEE YOU THERE ! ! !

↓ THESE POSITIONS ↓ NEED TO BE UPGRADED. LET’S DO THIS AT THE DE PAUL MEETING

Coordinators:

<>
ISPP Authors:        Art Schmidt                Data Base Managers:
              John Milton
              Pete Insley

Photographers:    Paul Dolan                Treasurers:
                          Art Schmidt
                          Gerry Lietz
                          John Milton
                          Earl Zwicker

Special Events Committees:
Physics Day –
John Rush Award –
Harald Jensen Award –
Annual Tri-Physics Meeting –
National Bridge Building Committee –
New Member Committee –

To get to DePaul University:

From the north and northwest

From the Kennedy Expressway (I-90/I-94) exit at Fullerton Avenue and turn left (east.) The Lincoln Park campus is
approximately two mile from the expressway on Fullerton Avenue at Kenmore Avenue.

From the west

From the Eisenhower Expressway (I-290), turn onto the Kennedy Expressway (I-90/I-94) heading toward Wisconsin. From the Kennedy Expressway (I-90/I-94) exit at Fullerton Avenue and turn right (east.). The Lincoln Park campus is approximately two miles from the expressway on Fullerton Avenue at Kenmore Avenue.

From the south

From the Dan Ryan Expressway (I-90/I-94) continue as the expressway becomes the Kennedy Expressway (I-90/I-94). Exit at Fullerton Avenue and turn right (east.) The Lincoln Park campus is approximately two miles from the expressway on Fullerton Avenue at Kenmore Avenue.

From Lake Shore Drive (north or south)

Exit Lake Shore Drive at Fullerton Avenue. Head west for approximately three miles. The Lincoln Park campus is located at
Fullerton Avenue at Kenmore Avenue.

If you use the Sheffield Avenue high-rise parking structure,
get a chit at the meeting that will cover the cost.

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