Sheri Donovan said in her original post on 9th grade physics, "What topics
would be best suited for such a course? What problems might we anticipate?"
Here is the second part of my response to these questions. Actually, it
isn't from me; rather, it's a post last spring to the modeling listserv by
Larry Dukerich, a high school teacher and CO-PI in our NSF grant: MODELING
INSTRUCTION IN HIGH SCHOOL PHYSICS.
Date: Sat, 20 Mar 1999
From: Larry Dukerich <dukerich@ASU.EDU>
Subject: physics first
Hi Folks,
After Leon Lederman came to ASU to discuss his "Physics First" initiative, I
asked Rex Rice (Phase I participant and Phase II leader) to tell us a bit
about what they do at his high school in Clayton, MO. You will find Rex's
remarks thought-provoking, whether or not you are seriously considering 9th
grade physics at your school.
I spoke with Rex Rice about the way they do physics first at Clayton HS in
Missouri. Below is a compilation of three emails that Rex sent me to
answer this question. You may find his account helpful should you wish to
implement a physics-first approach.
LD: I was wondering if you could provide us a brief outline of what it is
that you guys do with the 9th graders at your school.
RR: I try to do modeling, in a limited fashion, with my 9th graders. I
teach the "REGULAR" LEVEL FRESHMAN PHYSICS, so I am dealing with
approximately the "lower" two-thirds of the student body. With this group
of mostly average to below average students, I use the modeling method and
get through the following units:
UNIT I - (I don't include significant figures here... they just confuse
the issue) In unit I I am primarily interested in experimental design and
analysis. We do the pendulum lab as three separate experiments, but do
not, at this point worry about straightening graphs. We also do a spring
experiment, primarily to learn to do mathematical analysis of linear
graphs. We do not use the computers for graphing at this stage. I want
these guys to understand how to make a graph and particularly how to scale
a graph before I turn them loose on the computers.
UNIT II - This unit is done in its entirety. We actually do a total of
three different uniform motion experiments. We start with the BB in the
water-filled tube experiment (using two different angles for the tube),
followed by the car experiment (using two different speed cars) and
concluding with a glider on a level air track experiment (using two
different "pushes" to cause different speeds). The glider experiment is
videotaped and analyzed frame by frame. In each case both objects are
plotted on the same set of axes to emphasize the idea that the slope is
related to the speed of the object. There is a good deal of concept
development between each experiment with each one designed to reinforce the
ideas developed prior to it.
Students also use the motion detectors to try to reproduce several
different position vs. time graphs which contain only straight line
segments. We do work with some of the early parts of PAS Conceptual
Kinematics software in this unit as well.
I use most of the Unit II worksheets, but downplay the more
algebraically involved problems. These kids seem to do fine until they are
confronted with an equation that requires them to solve for a variable. At
that time, kids who have been with you the whole way get the "deer in the
headlights" look and unfortunately shut down. I learned in my first
iteration that minimizing the algebra required (even though all of these
students supposedly passed algebra as eighth graders) is a smart thing to
do. Lots of good physics still happens with a minimum of algebra. I do
not bypass this (algebraic problem solving) altogether, but I spend a
minimum amount of time on it and count it fairly lightly on exams. Some of
my kids can do it, but they are in the minority.
UNIT III - This is treated very similarly to Unit II. We do three
uniformly accelerated motion experiments. These include the wheel and axle
experiment (in lieu of the ball down the ramp). This is done using a
metronome as a timing device, so time is indeed the independent variable.
The second experiment is a glider on an inclined air track which is
videotaped and analyzed frame by frame. At the end of this unit we
introduce free fall as an application of uniform acceleration. We make
stroboscopic photographs of falling golf balls. Students analyze the
photograph and prepare a formal lab report.
More work is done in this unit with the motion detectors and
students moving relative to them to try to reproduce v vs. t graphs and
predicting what the corresponding position vs time and acceleration vs.
time graphs include. Problem solving is again simplified to avoid scaring
too many students off. 1-D Vectors ARE treated carefully in this unit and
do not seem to be a major problem. We use more of Conceptual Kinematics
and Graphs and Tracks in this unit.
UNIT IV/V - We do no trig in this unit. We do the introductory demo from
Unit IV and develop the concept of a force and force diagrams, the concept
of net force, and the relation of net force to motion. We also do the
Gravitational Force vs. Mass experiment and discuss the ideas of mass and
gravitational force carefully. We follow this with the Unit V paradigm lab
in order to develop Newton's second law.
We concentrate primarily on the effects of net force and mass on
acceleration through the remainder of the unit. Problems are chosen which
have only one body, and for which the net force can be determined through
the force diagram fairly easily. Again, no trig! No pulley problems like
Atwood's or "half-Atwoods" machines are done.
Finally in this unit, we do the paradigm experiment for Newton's
Third Law that Dave Braunschweig and I put together at UWRF. We make more
use of the Hewitt book and its various review and think & explain questions
in this unit.
And there you have it. The first semester of freshman physics as
taught by me at Clayton HS. This year, I really got bogged down and this
took us an extra few weeks into the second semester to complete.
In the second semester, we go ahead and do some work on significant
figures and scientific notation along with a little unit conversion.
We then proceed to the Energy Unit. Two years ago, I used the
"new" energy materials as they then existed with the freshmen. I was
happier with their understanding than I had ever been even with my juniors
and seniors. Since then I have been using this approach with ALL of my
classes, and feel that I am getting better at using this approach all of
the time. I am just starting this with this year's freshmen, and it is
going well. I have designed a spring that attaches to the PASCO dynamics
cart track that is easy enough to use and yields good enough results that I
have reconsidered my earlier reservations about the energy labs. Over the
course of the past two weeks, the freshmen have successfully done three
energy experiments and I have changed my mind.
They did the spring experiment with only one spring and set up so
that the F vs. x graph goes through the origin.
We then did an experiment in which they stored energy in the new
spring on the PASCO track, and measured, using a photogate and a flag on
the dynamics cart, the velocity of dynamics cart launched on a level track
by the spring. The energy vs. velocity squared graph had a slope that was
typically within 10% of one-half the mass of the cart, and closer to 5% for
the lab groups with really good technique.
They then did an experiment where they released a weighted card set
up as a pendulum from a series of heights (5 cm to 30 cm in 5 cm
increments). They measured the speed of the card using the length of the
card and a the time for it to pass through a photogate placed at the bottom
of the swing. They plotted a graph of gravitational energy (at the top of
the swing, relative to the bottom of the swing) vs. height. They assumed
that the gravitational energy at the top was equal to the kinetic energy at
the bottom, which they were able to calculate. This graph (Eg vs. h)
yields a slope that was well within 5% of the product of the mass of the
card and 9.8 N/kg.
With this series of experiments, we were able to develop
mathematical models for elastic energy in a hookean spring, kinetic energy,
and gravitational energy. Next I will see if they can apply these
mathematical models with the energy relations they write from their bar
graphs to solve for unknowns. I know this part will probably be less
successful because of their horrible algebra skills. I think that the set
of experiments will have been, nonetheless, fruitful.
With my JUNIORS AND SENIORS, I have done the experiment in which
the spring is compressed and used to launch a glider up an inclined air
track to relate gravitational energy to height, but the FRESHMEN do not
have the math to relate the distance along the track and the angle to the
height reached by the glider. The pendulum version seems to be a
satisfactory substitute.
Last year, using rubber bands and a different spring arrangement,
the best I was ever able to do on the slopes with excellent technique was
an error of about 13%. It was very hard, even for bright kids to figure
out whether the slope of the energy vs. velocity squared graph was supposed
to be the mass of the glider or one-half the mass of the cart, since it was
in the middle of the two. With this new spring, even on a dynamics cart
track, the freshmen seemed to have no problem realizing that it was
one-half the mass of the cart. I am pleased!
I need to tell you how I have modified the experiment using the air
track to get GREAT results). In any event, I use the energy materials
mostly qualitatively, and I feel that if students can write an appropriate
energy equation for various situations we have been successful. We do the
experiment relating the gravitional energy of a pendulum at the top of its
swing to the kinetic energy at the bottom quantitatively using photogates
and it works great with them.
We do not include projectiles, momentum, circular motion, or SHM in
our mechanics section.
I then follow mechanics with CASTLE. In the past I have followed
the materials as presented by Steinberg fairly faithfully through section
6. This year I plan to try the modified CASTLE materials. This is a good
unit for freshmen although they are pretty tired of it by the end of the
third section.
The next unit is electrostatics using the Bob Morse materials.
This is also a good unit for freshmen. We do not try to deal with this
quantitatively at all.
By the time we have finished with the above, there are usually
about six weeks left. I have traditionally done units on waves & sound and
a little bit with light in the remaining time. I try to do things that are
high interest to keep kids on task as the year draws to a close.
LD: Then, when you teach physics to juniors/seniors, you do revisit some
of the topics, no?
RR: Before I answer this question, I should explain what Bob Mullgardt
[Rex's colleague at Clayton HS] does with HONORS FRESHMAN PHYSICS.
In this course which is taken by the top quarter to third of our
freshmen, Bob teaches via what is basically a modeling method as well. The
course sequence follows what we traditionally used in the previous course
which was called Quantitative Science.
The first semester of Honors Freshman Physics is primarily
geometric optics. All of the major science skills are integrated into a
fairly detailed investigation of geometric optics. Each unit begins with a
paradigm experiment, and the models are developed in what is remarkably
close to our modeling cycle. The fundamental model used is a particle
model of light. No reference to a wave model.
The sequence includes:
Pinholes
The Law of Reflection and Plane Mirrors
Curved Mirrors
Refraction and Snell's Law
Lenses
Students learn to do graphical analysis extremely well. Bob
reserves computer graphing until the second semester.
During the second semester Bob has integrated very complete
versions of Units II and III. He does a Newton's Laws unit which includes
many of the elements of Units IV and V. He completes the year with an
energy unit. His focus has traditionally run toward machines as an
application and he has spent loads of time on levers and pulleys and such.
Last year I was
able to convince him to consider the new energy materials and he is trying
to incorporate them. I plan to work on him some more this year and hope to
get him to buy into them more thoroughly. I think he will.
As you can see from the abbreviated set of topics, students are
allowed to investigate thoroughly and leave with what I consider is an
excellent understanding of how to do science as well as the ability to
properly apply many fundamental models in physics.
Now on to your question, which is a complicated one.
First the easy answer.
In my AP PHYSICS, virtually every student has completed the Honors
Freshman Physics course. Some of the students are juniors, some are
seniors. Bob keeps the student's laboratory portfolios until they get to
the later physics course and I give these back to them at the start of the
course.
We make some serious time through kinematics and dynamics and
require no review of graphical analysis techniques. We revisit experiments
from the freshman year, and use these as a starting point. There are units
in each of the major areas which are part of the AP Physics B syllabus, but
Kinematics and Newton's Laws go fairly quickly. Students have a firm
foundation for the rest of Mechanics.
The other place that I gain ground from the freshman course is of
course in Geometric Optics. I give them a two-day review of the full
semester of optics that have already had. I then give them a set of
exercises to work over spring break and then a killer optics test after
spring break. They do well.
That course is the only way that I am able to do an AP Physics B
course that hits all of the topics on the syllabus and is still taught with
the laboratory as the focus. The course has a definite modeling flavor
although whiteboarding (especially of problems) is minimized severely to
save time.
More complicated is my REGULAR (JUNIOR/SENIOR COURSE). This class
has an interesting mixture of students which make figuring out what to do
an extreme challenge. Some of the students in this class have had the
Honors Freshman Physics course. Some of the students have had the regular
freshman physics course, but most of them have had other teachers (not me).
The rest of the students are those who entered the school from some other
school after their freshman year and have had no introduction to physics.
The result is that I feel compelled to do the complete modeling program
with the classes, but at a pace that is faster than what I would do with
students who had not had a previous course. What usually happens is that
the resulting course is too slow for the kids that had the honors course,
too fast for the kids that have had no physics, and about right for the
kids from the regular freshman physics course.
******************
Jane Jackson, Dir., Modeling Workshop Project
Box 871504, Dept.of Physics, ASU, Tempe, AZ 85287
480-965-8438/fax:965-7331. http://modeling.la.asu.edu
Genius must transform the world, that the world may produce more genius.