High School SMILE Meeting
21 March 2006

Information:

• Write-ups for academic year SMILE meetings for the current semester may be found at http://www.iit.edu/~johnsonp/acysmile.html, and write-ups from previous semesters are permanently located at http://www.iit.edu/~smile/biweekly.htm.
• Your hang tag for parking at IIT is valid in the parking lot by the Keating Gymnasium on Tuesday afternoons, 4-6:30 pm, until the end of the Spring semester 2006.  Be sure to put this hang tag on your inside rear view mirror when you park here.
• The Spring 2006 meeting of the AAPT [American Association of Physics Teachers] will be held on Saturday, 01 April 2006 at Chicago State University.  A focus topic at the meeting will be Using Physics Education Research to Guide Instruction. Further program details are available at the CSAAPT-06 website: http://www.neiu.edu/~csaapt/,.
• Earl Zwicker called attention to the article Off the Wall on the Physical Review Focus web page:  http://focus.aps.org/story/v17/st9.  It describes measurements of hot spots adjacent to a heated object, which occur as a result of  turbulent convection.
• The next ISPP Meeting will be held at Lake Forest College, on Tuesday, April 4th (the same date as next SMILE meeting) Attendance there will count as SMILE attendance next time. Ann Brandon will take a SMILE sign-up sheet to that meeting.
• For details on future meetings of the Illinois State Physics Project [ISPP] see their website: http://ispp.info.  For details concerning Physics Northwest meetings see their website:  https://www.edline.net/pages/Physics_Northwest.

Chris Etapa (Gunsalaus Academy)                       Information on a low-cost MSSE Program
Chris is enrolled in a Master of Science in Science Education degree program at De Paul University. A new group will be admitted into that program, which is funded by the National Science Foundation.  For more information on the program see the following website: http://csh.depaul.edu/academics/graduate/stem-studies/Pages/default.aspx.  The degree program requires 12 courses, with 1 course per academic year  term, and 2 short courses in the summer. Thanks, Chris

Fred Schaal (Lane Tech HS, mathematics)               Graphing Inverse Trig Functions
Fred noted that books don't tell how to graph inverse trig functions. Fred figured out a pretty good way to do it with a TI-83 calculator. He projected the Ti-83 screen on the wall for us to follow along with his method. He had written a little program to plot these functions. First Fred plotted the inverse sin and the plot looked reasonable. But the same method with the inverse cosine did not give a curve that made sense. Some adjustments were made in the graph scale, as suggested by the friendly crowd, and the inverse cosine curve looked better. Fred then tried the inverse tangent and it also looked reasonable. Interesting, Fred!

Fred Farnell (Lane Tech HS, physics)                       Kepler's Law Website
Fred found The Planetary Orbital Simulation website, from The University of Nebraska, Lincoln:  http://astro.unl.edu/naap/pos/animations/kepler.swf. It  presents a nice simulation/explanation of various aspects of Kepler's Laws and simulations of the orbits of the planets. Fred had put together a nice exercise based on the simulator:

• Introduction
  In this activity you will investigate the relationship between the orbital period of a planet as it moves around the Sun and the length of the semimajor axis of its orbit. We will use a computer simulation for this activity. In the simulation, you will measure the relative amount of time it takes planets in our solar system to complete one orbit around the Sun. You will also be given the length of the semimajor axis of the orbit for each planet.
• Procedure
  
  1. On the planetary orbital simulation website, click on the 1st Law tab and choose the following options:
     Show semimajor axis.
     Show center.
  2. Click on the 3rd Law tab and choose the following options:
     Show solar system orbits.
     Show labels of solar system orbits.
  3. Set animation rate to 0.025 yr/sec.
  4. Choose Mercury from the planet menu and click on OK.
  5. Click on the start animation button and observe Mercury moving along the orbit.
  6. Record the length of the semimajor axis, in AU, from information given on the screen.
  7. Use a stopwatch to measure the time it takes Mercury to complete one simulated orbit. record this time, in seconds, and the simulated orbital period.
  8. After the data for Mercury have been recorded, repeat the procedure for Venus, Earth, and Mars.
  9. Also collect data for Jupiter, but change the animation rate to 0.10 yr/sec before running the animation for Jupiter. Record the length of the semimajor axis and the time to complete one simulated orbit. When recording the simulated orbital period, multiply the measured time in seconds by 4 to adjust for the change in the animation time.
• Data
  Determine the semimajor axis length (R) and simulated orbital period (T) for the planets Mercury, Venus, Earth, Mars, and Jupiter.
• Analysis
  Determine these ratios involving the Orbital Period (T) and semimajor axis (R) for the planets Mercury, Venus, Earth, Mars, and Jupiter.
  • T/ R
  • T² / R
  • T² / R²
  • T² / R³
• Conclusion
  Discuss how the orbital period of a planet is related to the length of the semimajor axis of the orbit. Be specific and give examples from your data that support your conclusion.

The first example was Mercury, and the simulation clearly showed the details of the elliptical orbit. We displayed vectors for its velocity and acceleration, which changed continuously as the planet traversed the orbit; the correlation of this property with the change in velocity of the planet as it gets further away and closer to the sun could be clearly simulated by adjusting the orbital parameters. Kepler's Second Law (equal areas in equal times) could also be simulated in a very useful way.

Porter Johnson pointed out that the planet Pluto moves about the sun with a period that is precisely 3/2 that of the planet Neptune. Furthermore, there are several objects that move with this same period. For details see the website The Plutinos: http://www2.ess.ucla.edu/~jewitt/kb/plutino.html.  In addition, the planet Mercury rotates with a period of 2/3 of its orbital period about the sun:  http://cseligman.com/text/planets/mercuryrot.htm.
This is a very nice teaching tool! Thanks, Fred.

Roy Coleman (Morgan Park HS, retired)                Software
Roy called attention to the XnView website, http://www.xnview.com/, which contains free software for conversion of image files to various formats, such as JPEG, GIF, and TIF. Then he touted the Google Earth website, http://earth.google.com/, which contains free downloadable software of graphical images of the earth, with the capability of magnification and localization.
Neat! Thanks, Roy.

Larry Alofs (Kenwood HS, retired)             Piezoelectricity
Larry first showed us a little piezoelectric igniter, like those used in gas grills. Larry then showed us another version of the igniter (the "matchless pilot light"), and a third example (a cigarette lighter; it would also need butane as a fuel to ignite and burn). Each uses a crystal (of something Larry couldn't remember) which is encapsulated and can be squeezed at either end. Larry took the lighter apart for us, projecting the (small) parts on the screen using the overhead projector. A tiny hammer mechanism hits the crystal and causes the spark.

Larry then showed, using a homemade electroscope apparatus, that the crystal from one of the igniters, when it is compressed, can transfer charge to another object. It was done by transferring charge to two small strips of aluminum foil which were hanging together, suspended from a paper clip, causing them to repel each other. The harder Larry compressed the crystal, the more charge was transferred and the greater the repelling of the two aluminum foil strips.

For additional information on Piezoelectricity see the Wikipedia website:  http://en.wikipedia.org/wiki/Piezoelectricity#Crystal_classes, from which the following has been excerpted:

"Many materials exhibit the effect, including quartz analogue crystals like berlinite, gallium orthophosphate, ceramics, tungsten, barium titanate, strontium titanate, lead zirconate titanate, lithium niobate, lithium tantalate, sodium tungstate, ... . Materials like rubber, wool, wood fiber, and silk often behave as electrets. Although this phenomenon is often confused with piezoelectricity, the two phenomena are distinct. The orientation of polarization in a piezoelectric is limited by the symmetry, whereas the polarization direction in an electret is not. The polymer polyvinylidene fluoride, PVDF exhibits piezoelectricity several times larger than quartz. Bone exhibits some piezoelectric properties, due to the apatite crystals: it has been hypothesized that this is part of the mechanism of bone remodeling in response to stress, as the electric fields on the apatite crystals stimulate further bone growth."

Ann Brandon (Joliet West, retired)                    Math Puzzle (Kakuro) and Paper Clip Energy
Ann had us each take a paper clip and bend it into a triangle with one side of the triangle being formed from the two overlapping ends of the clip and held together by friction. When you drop it and the ends come apart, the potential energy stored in this configuration may be  released when it it hits the ground, and the triangle may jump back up. We didn't have a lot of success in our attempts to launch this device!

Ann then showed us two examples of a Kakuro puzzle, sort of like a crossword puzzle but with arithmetic sums (across and down) instead of words. You are not allowed to use the same numeral (1-9) in the same row or column of a given block.  Her puzzle was taken from the book Kakuto presented by New York Times puzzle editor Will Shortz --- one hundred addictive puzzles, St Martins Press 2006 (ISBN: 0-312r36042-8):  http://www.holtzbrinckpublishers.com/stmartins/search/SearchBookDisplay.asp?BookKey=4523318.  See also the book Kakuro for Dummies:  http://www.mcnallyrobinson.com/product.php?txtCatID=389&txtProdID=332997.  These puzzles can be quite difficult, since they cannot be completed one piece at a time!
Rather puzzling, Ann.

Bill Colson commented on the Mr Calm - Mr Angry optical illusion at the last meeting. Bill had gone to one of the web sites included in the newsletter. Bill said that the writer of one of the web sites explained that each image is overprinted with features at different resolutions, presumably features appearing and disappearing as you get closer to or farther away from the image.

Bill Shanks (Joliet Central, retired)                   Whistle Balloon Helicopter
Bill shared with us a favorite physics toy -- the Whistle Balloon Helicopter  http://www.costumes4less.com/products/kb125/Whistle_Balloon_Helicopter. It is also available as the Neato Balloon Helicopter.  It is great for illustrating Newton's Third Law. A balloon is inflated and attached to a little nozzle on a rotor with three blades. As the air comes out of the balloon, it causes the rotor to spin and you get a little helicopter that flies up. Look for it at toy stores or museum stores.
And off we go! Thanks, Bill.

Bud Schultz (Aurora Middle School)                        Leyden Jar
Bud brought in a Van de Graaff generator [http://www.amasci.com/emotor/vdg.html] and a homemade capacitor -- a Leyden Jar made from a plastic soup container, aluminum foil, and a bit of wire. For details see the website  http://www.alaska.net/~natnkell/leyden.htm.  Bud used the generator to charge the capacitor.  Next he disassembled the Leyden Jar, and gave the parts (aluminum foil, wife, plastic container) to Fred to examine.  He then put Leyden Jar back together and -- to our surprise -- it was still charged. Fred then discharged the capacitor through his finger.
Quite stimulating!  Thanks, Bud.

Our next SMILE meeting will be on Tuesday April 04, 2006. See you there!

Notes prepared by Ben Stark and Porter Johnson.