High School Math-Physics SMILE Meeting
22 February 2005
Notes Prepared by Porter Johnson
- Ann Brandon reminded us that the next meeting of
Section of the American Association of Physics Teachers [CSAAPT]
be held on Saturday 19 March 2005, 8:30 am to 1:30 pm, at Loyola
University Lakeshore Campus.
- Ann also reminded us that Physics Day at Great
America will be held
on Wednesday 11 May and Thursday 12 May, 2005. You may
online until March 31 at the following website: http://www.sixflags.com/greatAmerica/events/CalendarEvents.aspx.
- Earl Zwicker announced the continuing give-away of
equipment that is
no longer being used at IIT. In particular, setups of Turntable
Oscillator Systems were given to Ann Brandon and Charlotte
Wood-Harrington. These systems were invented by the late Harold
Jensen, our Phenomenological Guru and Mentor at
Forest College. The systems consist of two independently
phonograph turntables, and various
supports. They can be used to give a direct and illustration
of beats. Beats can be obtained because
the two turntables rotate at slightly different frequencies. It
heart-warming to know that this apparatus will be put to good use!
And, by the way, we hope to see a demonstration in the future.
- Porter Johnson appeared on the WGN-TV news on
February, concerning the constitution and construction of a
baseball. He appeared in connection with the announcement
by a local
restaurant to pulverize the contents of an infamous baseball and to use
a flavor enhancer. He commented that, in his opinion, the
interior would be "thoroughly unappetizing"!
- Roy Coleman presented Porter Johnson with
a genuine Physics
T-shirt that he had obtained from the American Association of
Teachers, which has an on-line catalog at this website: http://www.aapt.org/Store/.
On the back of the t-shirt was the header "Don't Drink and Derive ...",
underneath which the following equations, among others, appeared:
E = m c3 ... Sm
F a ... a = Dt / Dv
How kind and thoughtful of you, Roy!
Walter McDonald [CPS substitute
Walter presented us with two questions on Buoyancy from the book
1000 Play Thinks:
Games of Art, Science, and Mathematics by Ivan Moscovitch. For
the SMILE writeup of 24 September 2002: mp092402.html
. Walter provided a clear "fish tank" reservoir
filled with water, and we studied the questions and answers, drawing
as given below.
- Playthink # 872
- Question in book: "Will the time it takes for a
Ping-Pong ball to rise to the top of a cylinder of water be different
if the water in the cylinder is still or if it is swirling around?"
- Observations: We used a rectangular tank almost
filled with water, instead of a deep cylindrical tank. First we
put a Ping-Pong ball into the water, held it in place with metal tongs,
and then released it from the bottom. The ball quickly rose to
the top of the tank. We then put the water into rotation by stirring it
vigorously with a stick. We quickly inserted the Ping-Ping
ball into the swirling water, and released it. It quickly
rose to the top again.
- Answer in book: "The lightweight Ping-Pong ball
will rise very quickly in still water.
But when the water is agitated, the buoyancy of the ball is drastically
reduced. The movement of the liquid produces higher pressures
that make the displacement of the ball more difficult."
- Conclusion: We were unable to reproduce the
described results, and are not entirely convinced by the explanation,
since higher pressure differences, rather than merely higher
pressures, are needed to decrease buoyancy. Does this
really work as claimed?
- Playthink # 874
- Question in book: "Imagine you are in a bathtub
checking to see how much weight your toy duck can carry before it
sinks. You place a heavy metal ring on the duck, and it doesn't
sink. Then the ring slips off and falls to the bottom of the
tub. When the ring falls, does the water level in the tub go up,
go down, or stay the same?"
- Observations: Walter filled the tank
nearly full with water, floated a plastic bottle on its surface, and
carefully laid a heavy metal ring on the bottle. We carefully marked
the water level on the outside of the tank with a felt pen. We
then gently pushed the bottle, so that the metal ring would
fall off it and sink into the water. We repeated this experiment
several times, and the water level was seen to drop (by about 1
cm) each time.
- Answer in book: "According to Archimedes'
principle, an object floats because it displaces an amount of water
equal to the weight of the object. So to float when the ring was
placed on it, the duck must displace a volume of water that equals the
weight of the ring.
Since the metal ring is denser than water, the volume of displaced
water is greater than the volume of the ring. When the ring falls
in the water and sinks, it displaces only its own volume of water.
The water level, then, drops when the ring slips off the duck and into
- Conclusions: Full credit for a correct answer to
the Book Man. We agree!
Neat demos and good physics! Thanks, Walter!
Fred Schaal [Lane Tech HS,
Pump Up the Volume
V = L ´ W ´
(14.25 cm) ´ (14.15 cm) ´
(4.50 cm) = 907.36875 cm3 »
Of course, a
candy Aficionado or Gourmand would be more concerned about the
interior volume of
the box, which would be significantly less. We estimated the
be 10% to 20%. One could measure the interior volume of
the box by
seeing how much water it holds, using a graduated cylinder that holds
up to 1000
cm3 (one liter) of water.
Fred brought out a metallic box (appropriately decorated for
holiday gifts of candy or
sweets), along with a ruler. Fred recruited an
Wood-Harrington, to make measurements of its outside length L,
outside width W, and height H. Charlotte
following values: L = 14.25 cm, W = 14.15 cm, and H = 4.50 cm.
We then treated
the box as a Rectangular Parallelopiped, and computed its
Porter Johnson mentioned that glasses in restaurants, cafes,
and bars in
Europe are commonly marked to indicate the volume of a given
level of fluid. These markings,
which were a legal requirement in Germany, might be
one of the following:
| 0,3 L = 3 dL
|| 3 deciLiters, or 300 cm3
| 0,5 L = 5 dL
|| 5 deciLiters, or 500 cm3
| 1,0 L
||1 Liter, or 1000 cm3
Watch out for those one liter beer steins! Thanks, Fred!
Fred Farnell & Don Kanner [Lane Tech HS,
Fizzing Pop Bottles
Fred and Don investigated this burning scientific and societal
and why do soft drinks -- which are often called "pop" in
Wisconsin, "cold drinks" or just "coke" down South,
"soda" in New England, and "cola" or "limonade"
in Europe -- lose their FIZZ. They put this question
experimental test, brought out several plastic bottles (about a
capacity) of Coca Cola™ and Dr Pepper™. These
purchased bottles seemed to be about the same temperature and internal
since they felt "similar" when we squeezed them. First we
investigated the effects of (1) shaking the bottles a
vigorously, and then allowing their contents to settle for a few
(until the foam disappears), as well as (2) opening the plastic
caps slowly or
quickly. Here is a recording of some of our results:
Evidently, shaking the bottle tends to produce a more violent opening,
as does opening the cap quickly.
- \ -
| Not Shaken
a little bubbling
| Shaken Vigorously
Lots of foam
|Bottle #1: lots of foam
Bottle #2: very little foam
Just what causes the violent foaming? Through class discussion, we
the following points as likely to be relevant..
Don Kanner illustrated the phase rearrangement induced by
drinking about half of the contents of one of the Coke bottles,
the cap, and shaking it vigorously. When -- just as before -- the
was opened a little afterward, there was foam all over the
he repeated the process of tightening the cap, shaking the bottle, and
it several times, the amount of foaming decreased each time.
Finally, Don then
tasted the contents --- flat Coke! He had removed most of the
through this process. Several groups in the audience performed the same
experiments, drinking some of the contents with small cups that Don
provided, with the same conclusions. For a related discussion,
see the discussion of metal cans
of Guiness™ Stout by Charlotte Wood-Harrington at
meeting of 28 September 2004: mp092804.html.
- Most of the carbon dioxide (CO2) is dissolved
in the liquid as an ionic solution of carbonic acid (H2C03),
and only a small amount is present as C02 gas.
- When the bottle is opened (slowly or quickly), the gas pressure
inside the bottle
also decreases (slowly or quickly).
- When the bottle is shaken vigorously, some of the CO2
dissolved in the liquid becomes gaseous before
the bottle is opened. The foaming is a manifestation of this conversion
to the gaseous state. However,
even after the foaming disappears, a significant amount of gaseous
C02 may remain. In fact, it may take
an hour or so for that CO2 gas to re-dissolve in
- Curiously, bottles that look the same (bottle #1 and bottle
#2 in the table) may respond differently to vigorous shaking. The
amount of CO2 gas in the shaken bottle
depends upon the precise details of the shaking process. The shaking
process is a means to induce phase rearrangement that returns to
equilibrium quite slowly, in practice. It is quirky, in
Sweet science with sweet stuff! Thanks, Fred and Don!
- Q: What is the meaning of the numbers 10
-- 2 -- 4 on the traditional logo for Dr Pepper™?
- A: One possible interpretation is the
following: At 10 am you drink it; at 2 pm you become ill,
and at 4 pm you die.
Bud Schultz [Aurora West HS,
Dropping magnets through pipes, revisited
Bud recently obtained a set of 4 rather powerful Neodymium
#35287 for about $3 -- for a picture click here]
at a local outlet of American Science and Surplus [http://sciplus.com/].
These magnets were about 5 mm ´ 7
mm ´ 9 mm in size.
presentation was an extension of those given by Marilynn
Stone, Don Kanner,
and Bill Blunk, at the Math-Physics SMILE meeting
of 20 April 2004: mp042004.html.
them -- first 1, then 2, then 3 -- through a vertical copper
pipe 1.5 meters long, with an inside diameter about
12 mm --- standard half inch pipe. Its lower end was about 20
floor level. Here are the times that we recorded
for the magnets to descend and strike the floor, with various numbers
of magnets attached
The magnets fell very nicely without coming apart -- in fact it was
difficult to pull them
apart. The magnets were slowed down because of eddy currents
the conducting copper pipe, producing an opposing magnetic field to
slow down the magnets.
as described by Faraday's Law and Lenz's Law.
time of fall occurred with to two magnets. As the number of
magnets in the
array is increased, the falling time changes because of the
increased weight of the array
and increased opposing eddy current forces.
|Number of Magnets
|| Descent Time
Bill Blunk repeated his
demonstration of the Math-Physics SMILE meetings of 20
April 2004 and of
08 September 1988 ph090898.htm,
dropping an aluminum parking token through
two pairs of magnets -- a configuration commonly found in coin-operated
Ann Brandon mentioned that, at a recent meeting of the
Illinois Section of the American Association
of Physics Teachers [http://helios.augustana.edu/isaapt/]
at UIUC, a magnet was dropped through a translucent plastic
LED's attached across
wire coils, which had been wrapped closely around the plastic pipe at
locations. As the magnet passed inside the pipe and through a given
the corresponding LED would flash. Now, there's Faraday's
Law for all to see!
Isn't that the Cat's Meow!
An excellent phenomenological exercise! Thanks, Bud!
Bill Shanks [Joliet and New Lenox environs, retired]
Bill showed off a new laser that he had obtained as a
"remainder" at a Cummins Tools store:
The device contained a red laser beam driven by 3 button cell batteries,
a hologram of a swan attachable to the front, a sonic
a Green Flashing LED. On the package it said "This is
toy!" -- but -- "Why does it chirp like a bird?"
We attached the hologram to the front, and looked at the resulting
pattern. Then we compared it with a more powerful and more
Green Laser provided by Bill Blunk. Interestingly,
see the path of the Green Laser beam more readily than the red
especially by standing behind it and looking within
about 10 degrees of its direction. Of course, both
were easily visible when chalk dust was scattered along the paths of
Very impressive gadgets! Thanks, Bill!
Notes prepared by Porter Johnson