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CoolStuff
Newsletter Article
Vol. 6, November 2002
Introducing
Newton's Laws with Learning Cycles |
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As many of you know, the Learning Cycle is an
approach to science instruction developed by Atkin and Karplus in 1962 while
working on the SCIS (Science Curriculum Improvement Study) project. This
approach puts the phenomena first. Names and numbers are brought into the
picture only after students are allowed direct contact with the phenomena.
Although there are a number of variations on the theme, the essential
learning cycle consists of three phases. These phases include exploration,
concept development and
application.
The "Learning Cycle" method may be used
to teach virtually any topic in physics and that includes Newton's Laws.
The forces exploration consists of a “smorgasbord” of twelve activities
relating to Newtons laws. This exploratory’s emphasis is on the introduction of
Newton's 1st, 2nd and 3rd laws.
At each station students are asked to perform
one or more activities and answer questions based on their observations.
These stations use a variety of manipulatives. Some stations feature common
household items; others use either commercial devices or teacher-produced
apparatus. I would like to share some of our students’ favorite stations
with you. During the last 30 years, Dr. James Hicks and I have assembled
exploratory activities that we’ve used to introduce each major topic (for
example, forces, energy, optics, wave phenomena, electricity, magnetism,
etc.) in our physics classes. These collections contain both time-honored
“experiments” and activities that Jim and I have concocted or borrowed from
our students or other teachers. If you would like to use this idea in your classroom, you can
download the PDF file containing the details of each station
(PDF download is available at the
bottom of this newsletter). I like to
print and laminate the description and questions and then post them at each
station. Here are some guidelines for the "Newton Adventure":
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An exploratory is a collection of
introductory science activities that relate to a single topic or concept.
Exploratories provide students with a common experiential base while
igniting their interest.
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The activities are arranged as numbered
stations around the room. Manipulatives at each station provide
opportunities for exploration and discovery.
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The exploratory uses a guided inquiry
approach. The guidance is provided through instructions and questions
that accompany each station. The teacher remains in the background and
assists only when asked.
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The activities may be done in any
order.
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A non-judgmental approach is used. At
this point, the teacher should be focusing on the quality of a student’s
reasoning, not whether an answer is right or wrong. The teacher is given
an opportunity to listen to students dialog with peers and formulate
explanations. Student pre-conceptions are revealed during this phase of
the learning cycle.
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Exploratories encourage student
engagement. Intriguing manipulatives tend to get even the most
disinterested students involved. Since discrepant events leave the
students with a need to know, the class discussion that follows an
exploratory is teacher led, but student-driven.
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Exploratories provide qualitative
experiences. Quantitative laboratory work is done later.
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Placing instructions at each station
eliminates duplicating costs. Laminating the instructions allows them to
be reused.
~Chris Chiaverina |
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Newton's
1st law (a.k.a., Galileo’s Law of
Inertia.) |
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Not with my dishes you don't!
Station 1
Haven’t you always wanted to try the old table cloth and dishes trick? To
perform this time-honored magician’s trick, place some old dishes (you may
want to begin with a single plate) on a smooth tablecloth. Grab both ends of
the tablecloth and, without hesitation, pull the tablecloth out from under
the dishes as quickly as you can.
Questions:
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Was it magic or physics? In other words, why did the dishes remain
virtually motionless when the tablecloth was quickly pulled out from under
them?
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Did the dishes move at all? Why?
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Why was a smooth tablecloth used? What do you think would happen if a
rough material, e.g. sandpaper, were used?
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The Physics Van Outreach program
http://van.hep.uiuc.edu
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Tee off time...
Station 2
Balance an embroidery hoop on
the mouth of an empty flask or glass soda or catsup bottle (see photo).
Now place an inverted golf tee on the top of the hoop. Note: a piece of
chalk with a flat bottom also works well. Make certain that the tee is
directly over the mouth of the bottle. Now take a deep breath, and remove
the hoop by quickly grabbing the inside center of the hoop.
Questions:
i) What happened to the tee?
ii) Why did the tee drop into
the container?
iii) Repeat the experiment,
this time quickly grab the outside of the hoop. What happens now? Can you
explain your observation? That is, why does the tee only fall straight down when
the hoop is grabbed on the inside?
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Looking Back...
Station 3
Bend
a stiff piece of wire, such as a coat hanger, into the shape shown in the
figure. Using two sticks of modeling clay, fashion two spheres of clay
around each end of the wire. Balance the center point of the wire on the
top of your head. Make certain that the wire frame does not come in contact
with your ears. Now quickly spin around.
Questions:
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From The Physics Classroom
Online high school physics
tutorials
http://www.physicsclassroom.com/
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Egg Pizza...
Station 4
Fill a medium sized beaker, wide-mouth glass,
or coffee cup 1/2 full with water. Place the container, a pizza pan, a
cardboard cylinder fashioned from a file card, and a hard-boiled egg near
the edge of a table as is shown in the figure. The egg and cylinder must be
directly over the beaker. Also, the pizza pan must extend beyond the edge of
the table. Believe it or not, the object of this activity is to knock the
pizza pan and cardboard cylinder out from under the egg so that the egg will
fall straight down into the beaker!
To accomplish this feat, a broom will be used
as a pizza pan “launcher.” Place the broom handle next to the edge of the
pizza pan. With your foot on the bristles of the broom, “cock” the broom by
pulling the handle away from the pan. This will put the handle under
tension. Now, without hesitation, release the handle. With luck, the egg
should drop into the beaker. For a greater challenge, increase the number
of eggs, beakers, etc.
Questions:
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Why
did the egg fall straight down and not move with the cardboard cylinder and
pizza pan?
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Do you think the mass of the object placed
on the cylinder matters? Please explain your reasoning. You may wish to
check your answer by replacing the egg with a ping pong ball.
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Egg Spin!
Station 5
In
this “eggsperiment” you will use two eggs, one marked with an “O”, the other
with an “X.” Spin the egg marked with an “X.” Now stop the egg with your
hand. Immediately after the egg stops, remove your hand. Describe what
happens.
Now
spin the egg marked with an “O.” Again stop the egg with your hand and then
quickly release it. Describes what happens this time.
(Teacher's note: One egg is raw and
the other is hardboiled)
Questions:
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 Click here
to
get information on
the Strobe Revolution |
Revolution...
Station 6
Give the “Strobe Revolution” a gentle spin and
watch it continue spinning in a state of near perpetual motion. Amazing!
Questions:
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Does the spinning axle eventually come to
rest? Why?
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If
all frictional forces could be eliminated, how long do you think the axle
would spin?
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Newton's 2nd Law |
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Jelly Jar Accelerometer
Station 7
An accelerometer is a device that may be used
to determine the direction of an object's acceleration. An accelerometer
also gives the direction of any unbalanced force acting on an object. There
are many types of accelerometers. One of the simplest is made out of a jar,
a bobber and some string.
Teachers Note:
To construct an accelerometer, glue
a string to the inside center of the lid of a jelly or peanut butter jar.
The length of the string should be slightly less than the height of the
jar. For reasons of safety, a plastic jar is always preferable. Attach a
plastic bobber to the free end of string. After filling the jar with water,
with the bobber and string on the surface of the water, place the lid on the
jar. Now tighten the lid and invert the jar. The bobber should now be
located just below the glass bottom of the jar. If it's dragging on the
glass bottom, remove the lid and slide the bobber along the string so that
it is closer to the lid. You are now ready to use your accelerometer.
Questions:
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Hold the accelerometer in your hand.
Which way does the bobber point when you are standing still?
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Which way does the bobber point as you
walk at a smooth, constant rate?
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Watch the bobber as you start from
rest and accelerate to the right. Which way did it point as you picked up
speed? As you slowed down to a stop? You may have to repeat this part of
the experiment several times in order to see all that's going on.
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Repeat part (iii), this time
accelerating to the left.
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How does the direction of the
unbalanced force you are exerting on the accelerometer with your hand
compare to the direction of acceleration?
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Holding the accelerometer in front of
you at arm's length, spin in a circle. (Be careful not to get too dizzy!)
Observe the direction in which the bobber is pointing. According to the
accelerometer, what is the direction of the jar's acceleration? In which
direction are you exerting an unbalanced force on the jar?
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Newton's 3rd Law |
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That's Repulsive!
Station 8
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Obtain two small magnets. Can you make the two
magnets attract each other?
Repel each other? Place the two magnets on the table and align them so that
they repel each other. Bring them close together and then release them.
Questions:
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Describe what you observe.
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Does each magnet exert a push on the other magnet?
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How do you know?
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Compare the strength of the two forces.
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Arrange two small magnets so that they attract each other. Separate the
magnets so they are one or two centimeters apart and then release them.
Questions:
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Describe what you observe.
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Does each magnet exert a pull on the other magnet? How do you know?
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Compare the strength of the two forces.
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So Attractive?
Station 9
Click here
to
get information on
assorted Magnets |
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Tug-of-War!
Station 10
Click here
to
get information on
Spring Scales |
Using two spring scales, have a tame “tug of war” with your partner. Observe
the readings on the two scales during the tug of war (don’t pull too hard!).
Questions:
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Describe the readings on the scales.
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Can you and your partner pull in a way that will produce a higher
reading on one scale than the other?
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Can you and your partner pull in a way that will produce a reading of
zero on one scale but not on the other?
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Explain your answer.
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With your lab partner, hold two bathroom scales back to back. Now push on
the scales and observe both readings.
Questions:
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How do the readings compare?
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Can you and your partner push in a way that will produce a higher
reading on one scale than the other?
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Summarize your findings from stations 10 and 11.
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The Big Push...
Station 11
Click here
to
get information on
Bath Scales |
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Up Up & Away!
Station 12
Click here
to
get information on
the Balloon Helicopter |
The Balloon Helicopter is a toy Newton would have loved! Blow up the balloon
and attach the hub to the blade assembly. Now release the helicopter and
watch it go!
Questions:
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Why do you think the helicopter flies?
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Do the helicopter’s blades push on the surrounding air? How do you know
this?
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Does the air surrounding the blades push on the blades?
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Which of these
two forces causes the helicopter’s motion?
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Would a helicopter fly in outer space where there is no atmosphere?
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Concept Development
The students have completed the exploratory.
What's next? During the next segment of the learning cycle, the concept
development phase, basic principles emerge, terminology is introduced, and
mathematical relationships are derived. With the teacher serving as a
guide, students construct meaning from observations made during the
exploratory. How is this accomplished?
I generally engage students in class discussion immediately after their
laboratory activity. The wonderful news is that students do not have to be
coaxed into participating. The exploratory almost always leaves kids with
unanswered questions. This produces what Piaget referred to as
disequilibrium. In this state, students have a need to know and are
motivated to ask questions. This phase is particularly exciting because the
teacher and students are given an opportunity to listen to each other's
explanations. With the guidance of the teacher, meaning and understanding
begin to emerge from conflicting ideas.
In addition to discussion, a variety of methodologies may be employed during
this concept development stage of the learning cycle. They include reading,
computer work, or demonstrations. At this time, it may even be appropriate
for the students to return to the laboratory to test a hypothesis that was
brought up during class discussion.
Application
During the last phase of the learning cycle,
students return to the laboratory where they engage in real-life
applications of their newly acquired knowledge. These activities may be done
in a conventional laboratory or in some rather unorthodox settings.
Regardless of the venue, students apply the physics they have just learned
in a meaningful and quantitative way.
For the last 25 years we've had students push cars with bathroom scales in
the school’s parking lot as an application of Newton's Second Law of Motion.
The bathroom scales provide a known force and regularly dropped safety cones
are used to obtain the vehicle's acceleration. We use the acceleration and
force to calculate the vehicle's mass. While this may seem a little
strange, it illustrates to students that the material studied in class
pertains to objects both small and large. Of course students always want to
push things to the limit and this annual event is certainly no exception.
Each year I ask students to bring in their own cars for the lab. I usually
get cars ranging from a sub compact to a SUV. A few years ago a student said
he could arrange for a couple of vehicles that might be interesting to use,
but he wasn't saying what he had in mind. When my class convened in the
parking lot the next day, there sat a school bus and a Hummer ready to be
pushed. Mind you, this was when the Hummer had just become commercially
available. Not only did my students go wild, but there were cheering
students, teachers and administrators leaning out of every single window of
our four-story school.
As my students pushed the two "monsters of the midway" and a variety of
other cars and trucks, hundreds of witnesses saw Newton come through one
more time. It might be said that conventional learning went out the window
for a while that day, but the force was certainly with real-life physics! |
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Next Issue:
As I mentioned at the beginning of this
newsletter, the learning cycle may be used to teach virtually any physics
topic. In the next edition of Cool Stuff, I will present a dozen
exploratory activities that may be used to introduce the concept of energy.
Until next issue....
Regards,
ABOUT
: Chris
Chiaverina has been teaching physics for 33 years, the last 11 at New Trier
High School outside of Chicago. In 1997 Chris was presented with the
“Excellence in Pre College Teaching Award" by the American Association of
Physics Teachers. He is currently serving as president of that group. He is
coauthor of the book “Light Science” and has given numerous presentations
around the world. |
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