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Part of the problem is that the texts emphasize using algebra to solve
problems. However, many difficult problems can not be solved by
algebra. The Minds on Physics series activity 16 is specifically
designed to present a problem which can not be easily solved by
algebra, but is very easily solved using either a graph or strobe
(motion) diagram. If students were introduced to these before
algebra, they would then more readily understand the algebra. Indeed
the strobe diagram can be used by middle school students to readily
solve all kinds of rate problems and they understand the method very
well. It might even be possible to introduce it late in elementary
school.
Once students have learned to solve problems using graphical methods,
then algebra is much easier. In particular the SVT equations are the
kiss of death because they reduce problem solving to the level of just
hunting for variables. Even some of the well known PER curricula do
not do enough with non algebraic methods of solving problems.
Apropos the problems of teacher training see the latest issue of Am.
Jour. Physics for the article by Shafer and McDermott.
John M. Clement
Houston, TX
I feel compelled to chime in. I teach high school and you are
right,
students don't know what a graphs are for or how to set them up
correctly.
In my classes, they learn this and they have to graph by hand. They
learn
the different relationships shown be the graphs and how to write
equations
from them. They have no clue about this before my class. They have
to
figure our how to get a slope when the graph doesn't have a straight
line but
a curve - which we go over very thoroughly. When they graph in
math, it is
just numbers and x and y axes - no labels, etc. They are amazed at
how you
can get an equation from the graph. If they have done any graphing
in
previous science classes, it was never shown to them what the graphs
are
really conveying and how much info you can get from a graph. They
do graphs
by hand until they show that they know and understand what they are
doing.
Only then do we move to graphing on the computer. They know that if
something isn't on the graph when they print it, then they better
write it on
or fix it and reprint it. We use Graphical Analysis and it really
is nice
for this. When you fit the line it does extend it to the vertical
axis AND
it gives you the slope and y-intercept.
So at least when students leave my class, they understand the value
of graphs
and they can make good graphs. But, as stated by others, not all
high school
teachers have been trained/made cognizant or whatever of PER and
they are
stuck in the old way of lecture only type of teaching. Even newer
teachers
don't seem well-prepared in this aspect and I blame that on
education
schools/courses. They don't seem to be aware of the research on
physics
education unless they are at an institute that is very involved in
it. It
doesn't help that the math classes are totally disconnected too.
--
Julie Hilsenteger
Physics Teacher
Centennial High School
3505 SE 182nd
Gresham, OR 97030
503-661-7612
julie_hilsenteger@centennial.k12.or.us