Aps-ajp-11-1001-Book indb

III. NEED FOR SPECIAL PHYSICS COURSES FOR 
K-12 TEACHERS GUIDED BY PHYSICS EDUCATION 
RESEARCH 
The other two papers on teacher preparation reprinted here 
were published in 1990 and 2006, respectively, long after 
the paper on the combined course. Together they describe 
the need for in-depth preparation of teachers in physics and 
comment on how we determine through research whether the 
instructional strategies that we develop are effective. 
The 1990 paper begins by summarizing the history of K-12 
science education in the U.S. and describes the ongoing lack 
of appropriate preparation for teachers at all levels of instruc-
tion. A strong case is made for physics departments to offer 
special courses for both preservice and inservice teachers. 
The 2006 paper supports these recommendations by illustrat-
ing the mismatch between standard topics in the K-12 cur-
riculum and the physics knowledge of many teachers. The 
following examples are in the context of balancing, kinemat-
ics (acceleration), electric circuits, dynamics, and geometri-
cal optics.
Elementary school curricula often include a unit on bal-
ancing. About 50 elementary school teachers (many of 
whom had taught this topic) were shown a diagram of a 
baseball bat balanced on a fi nger placed closer to the wide 
APS-AJP-11-1001-Book.indb 25
APS-AJP-11-1001-Book.indb 25
27/12/11 2:56 PM
27/12/11 2:56 PM

---

26 
Teacher Education in Physics
Summary: McDermott, et al.
end of the bat. They were told that the bat was of uniform 
mass density and asked to compare the total mass to the left 
and right of the balance point. Only about 15% of the K-5 
teachers responded correctly. Nearly everyone who gave an 
incorrect answer claimed there must be equal mass on both 
sides. They did not seem to be aware that it is not only the 
amount of mass but also its distribution that determines the 
turning effect.
A question to probe understanding of acceleration was 
administered to about 180 preservice and inservice teachers 
(primarily grades 9–12). The question was based on a strobe 
diagram of a ball rolling up and down an inclined ramp. Only 
about 50% of the teachers drew correct sketches that showed 
acceleration vectors of constant magnitude that were always 
directed down the ramp. The most common incorrect answers 
were that the acceleration would be zero at the turnaround 
point or directed vertically downward, rather than always 
along the ramp. 
The topic of electric circuits is included in many precol-
lege curricula. We have frequently asked for the ranking of 
the brightness of identical bulbs in three circuits with iden-
tical, ideal batteries. The circuits contain, respectively, one 
bulb, two bulbs in series, and two bulbs in parallel. The cor-
rect ranking is that the single bulb and the two in parallel are 
equally bright and brighter than the two in series. Of the many 
teachers who have been asked this question, only about 15% 
have given a correct ranking. Research has revealed two wide-
spread mistaken beliefs: (1) the battery is a constant current 
source and (2) current is “used up” in a circuit. 
Our development of an instructional sequence in the 
Dynamics module in Physics by Inquiry was motivated by the 
inability of many students to apply Newton’s Laws properly. 
In one example, students were shown a diagram of a sys-
tem consisting of three blocks in horizontal contact with one 
another. A hand pushes horizontally on one of the end blocks, 
thus accelerating the system. The question asked was how, if 
at all, the acceleration changes if the middle block is replaced 
by one of greater mass while the hand exerts the same horizon-
tal force. To answer that the acceleration has decreased, stu-
dents must recognize that the inertial mass has increased while 
the net force exerted on the blocks has remained the same. 
When this question was administered after standard instruc-
tion in introductory physics, fewer than 20% of the students 
answered correctly. The question has also been given to intro-
ductory physics students (N > 100) after they have worked 
through the tutorial on Newton’s Second and Third Laws in 
Tutorials in Introductory Physics, our supplementary curricu-
lum in which the treatment of Newton’s Laws is less thorough 
than in Physics by Inquiry.
7
 About 55% (N ~ 720) gave correct 
responses. While this improvement (i.e., 20% to 55%) is sig-
nifi cant, high school teachers must understand the material at a 
deeper level than students in an introductory university course. 
About 90% of the teachers (N = 45) who worked through the 
Dynamics module in PbI gave a correct response.
The research paper also contains an example from geometri-
cal optics that demonstrates the positive effect that even inex-
perienced teachers can have when they understand the material 
in depth. Their study of this topic begins with a pretest on the 
image produced by a triangular hole in a mask placed between 
a long-fi lament bulb and a screen. Like introductory physics 
students, only about 20% of our teachers have responded cor-
rectly. Most have had no mental model in which light rays travel 
in straight lines in all directions from every point on an object. 
After working through the Light and Color module in PbI, the 
teachers develop a ray model that enables them to account for 
the patterns formed by light sources and apertures of various 
shapes. After teaching this topic in a ninth-grade classroom, 
the preservice teachers have given a post-test. About 45% of 
their students have given correct answers. If the teachers had 
not developed a ray model, their students would likely have 
done no better than they had done on the pretest. 
When research in physics education has a strong discipli-
nary focus, it can signifi cantly contribute to the preparation 
and professional development of precollege teachers. The 
research summarized in this article should help convince 
university faculty about the type of preparation in phys-
ics that teachers need. The article also contains data from 
other populations, which are a resource that instructors can 
draw upon in teaching students at the introductory level and 
beyond.
1
The 2006 article accompanied an editorial that described in detail some gen-
eral issues relevant to physics teacher preparation that are described in this 
summary. See, Lillian C. McDermott, “Editorial: Preparing K-12 teachers in 
physics: Insights from history, experience, and research,” Am. J. Phys. 74, 
758-762 (2006).
2
At the elementary school level, the curricula included Elementary Science 
Study (ESS), Science Curriculum Improvement Study (SCIS), and Science – A 
Process Approach (SAPA).
3
A. Arons wrote The Various Language (Oxford University Press, NY, 1977) 
while teaching this course.
4
L.C. McDermott and the Physics Education Group at the University 
of Washington, Physics by Inquiry (John Wiley & Sons, NY, 1996). 
Development of the published curriculum began in the combined course.
5
These were initially inspired by the clinical interviews of J. Piaget, a Swiss 
psychologist.
6
D.E. Trowbridge and L.C. McDermott, “Investigation of student under-
standing of the concept of velocity in one dimension,” Am. J. Phys. 48 (12) 
1020-1028 (1980); D.E. Trowbridge and L.C. McDermott, “Investigation of 
student understanding of the concept of acceleration in one dimension,” ibid. 
49 (3) 242-253 (1981). These articles were the fi rst in AJP resulting from 
research toward a physics Ph.D. in a U.S. physics department. 
7
L.C. McDermott, P.S. Shaffer and the Physics Education Group at the 
University of Washington, Tutorials in Introductory Physics, First Edition 
(Prentice Hall, Upper Sadddle River, NJ, 2002); Instructor’s Guide, 2003. A 
Preliminary Edition was published in 1998.
APS-AJP-11-1001-Book.indb 26
APS-AJP-11-1001-Book.indb 26
27/12/11 2:56 PM
27/12/11 2:56 PM

---

Summary: Marshall and Dorward
Teacher Education in Physics 
27