For generations, teaching physics has been more about manipulating math problems than learning the basic principles that guide the discipline. That鈥檚 precisely why, according to a growing body of research, even students who aced physics courses often don鈥檛 understand the field.
鈥淭hey can use formulas, but they really can鈥檛 put together鈥攙ery well, anyway鈥� meaningful concepts,鈥� said Fredrick M. Stein, the director of education and outreach for the American Physical Society, a 43,000-member group of physics teachers and researchers based in College Park, Md.
But based on studies conducted over the past 25 years, physics teachers are slowly turning away from lectures highlighting the formulas derived from Newton鈥檚 laws of motion and other tenets. Instead, they鈥檙e presenting opportunities for students to see those laws in action and encouraging them to think like the scientists who discovered them some 400 years ago.
Physics is one field in which research has yielded 鈥渦sable鈥� information that teachers can apply in the classroom鈥攁 growing emphasis for many leading players in the world of educational research.
The knowledge acquired since physicists started probing how students learn their discipline has yielded a wealth of tips for instructional approaches that ensure students learn the concepts as well as the mathematics. And it is just now beginning to yield textbooks and curricula that give teachers the tools to translate research into practice.
High school teachers are 鈥渟tarting to get the message,鈥� said Jose P. Mestre, a physics professor at the University of Massachusetts at Amherst. 鈥淚t鈥檚 slowly but surely having an impact.鈥�
Working in Two Worlds
Unlike research in most other subjects, studies on how students learn physics have been conducted by scholars who have earned doctorates in physics and don鈥檛 have backgrounds in educational theory.
Because physics is divided between theoretical and applied branches, physicists have experience with both types of research and are comfortable developing theories of how to teach the discipline better, and then testing them with their own classroom instruction, says Gerald F. Wheeler, the executive director of the National Science Teachers Association, a 53,000- member group in Arlington, Va. Mr. Wheeler is a former high school teacher with a Ph.D. in nuclear physics.
Another reason for physicists鈥� interest is that education researchers have typically concentrated on issues with a wider impact throughout K-12 schooling, physics education researchers say. Physics, in contrast, is taught in high schools, and usually taken only by college-bound students.
鈥淭he education community has focused on issues with great leverage at the early stages, and it leaves us out in the cold,鈥� said Edward 鈥淛oe鈥� F. Redish, a professor of physics at the University of Maryland College Park. 鈥淭he education community has bigger fish to fry than just physics.鈥�
Mr. Redish heads the Physics Education Research Group at the University of Maryland. Similar efforts at the University of Washington, in Seattle; Arizona State University, in Tempe; and the University of Massachusetts at Amherst have contributed to the knowledge of how to teach physics so that students really understand it.
One word problem testing students鈥� knowledge of the concept of force shows why physicists have been working to improve the way they teach: If a truck hits a parked car that is half its size, which vehicle experiences the greater force?
Students鈥� intuition suggests that the car does; after all, it experiences the greater damage. But that answer contradicts Newton鈥檚 third law of motion, which says that for every action there is an equal and opposite reaction. In other words, the force felt by the two vehicles is the same.
Large numbers of students who are capable of doing the algebraic applications of Newton鈥檚 laws, researchers say, will give the wrong answer to the question.
The challenge for teachers, then, is to help those students understand the scientific reasons the car fares worse in the collision. A physics teacher can turn such questions into a lesson on Newton鈥檚 laws and how they apply, they say.
Andrew Elby, a former high school teacher who is now an assistant research scientist at the University of Maryland College Park, poses the question to students and then asks them to re-create it in a lab.
The students eventually are told to calculate the acceleration of the car and the truck using Newton鈥檚 second law, which says that a force is equal to the object鈥檚 mass multiplied by its acceleration.
Through a quick algebraic manipulation, if they assume that the two forces are the same, they can calculate that the car is accelerating twice as fast as the truck.
The exercise helps students understand that the car鈥檚 damage is caused by the rapid change in velocity when the truck hits it鈥攏ot the force of the collision, Mr. Elby says. He used the lab when he taught at high schools in San Francisco and suburban Washington.
鈥淭he idea is to refine their common-sense ideas so they鈥檙e able to explain them on their own terms,鈥� Mr. Elby said.
While the lab is instrumental in that process, it is only a starting point, he added. Other students understand the concept only after several class discussions of the lab and homework assignments prompting them to elaborate on their findings.
Such lab experiences are designed specifically to change students鈥� misconceptions about scientific principles鈥攁 crucial aspect of all scientific instruction. Because most students come to science class with assumptions about how the world works, those ideas stick with them until teachers disprove them convincingly.
鈥淧eople don鈥檛 move away from their misconceptions unless they have a reason to move away from them,鈥� said Mr. Wheeler of the science teachers鈥� association.
Too often, researchers say, teachers lecture about physics, explaining the theories in depth. But the only thing they write on the board is the formulas that express those theories in mathematical terms.
Light on Theories
What students walk out of the lectures with are notebooks heavy on formulas and light on theories, according to Mr. Mestre, the University of Massachusetts professor. Their homework and exams are full of problems that require them to use those formulas.
To change that brand of instruction, Mr. Mestre requires his students in introductory physics courses to answer every question by stating the main concept that applies in every problem and to justify their answers. Then they do the math.
鈥淭he students don鈥檛 like it,鈥� he said. 鈥淭hey鈥檇 rather just do the math.鈥�
Mr. Redish of the University of Maryland said that about 70 percent of his tests to college students are essay questions. The format requires students to understand the concepts of physics as well as the application of them, he said.
鈥淲e鈥檙e sending a very different message鈥� from the traditional algebraic approach, he said. 鈥淎 significant fraction of my students after one semester know what it means to understand physics.鈥�
Research projects have documented that student achievement improves with the types of instruction championed by physics researchers.
A multiple-choice test called the Force Concept Inventory, which assesses conceptual knowledge of Newtonian physics, is given to students before they start their first physics course and after they complete it.
Students in research-based courses generally show greater improvement in understanding the basic concepts of force, and outperform students who learned in a traditional, mathematics-based course.
On tests that assess problem- solving skills requiring mathematical thinking, students from courses that emphasize concepts score at least as well as those in the math-centered approach, according to Mr. Elby.
Aiming for an Impact
While physics education researchers have made strides in understanding how best to teach the subject, their findings haven鈥檛 yet gained much of a foothold in American high school classrooms. The influence has been greater in introductory college courses, researchers say, because much of the research is conducted by professors who apply their findings in their own classes.
鈥淲e鈥檙e still a long way from making the connection between research and [high school] classroom practice,鈥� said Mr. Wheeler.
But physicists are working to change the way future teachers are taught, in both science and education courses. Through a $6.3 million federal grant, the American Physical Society is leading a project in which the physics departments and education schools at seven universities are working together to put the lessons from physics education research into practice.
鈥淯ntil we can change the way we teach the teachers, we鈥檙e not going to see all of this carrying down to the K-12 schools,鈥� said Warren W. Hein, the associate executive officer of the American Association of Physics Teachers, an organization of 10,500 college and precollegiate teachers.
The association is a partner in the project with the American Physical Society and the American Institutes of Physics. All three groups are based in College Park, Md.
To take part in the Physics Teacher Education Coalition, or PhysTEC, physicists and teacher education professors must work together to model research-based practices. Physics professors must promise to teach prospective teachers in the manner supported by research. Physicists also must supervise prospective teachers鈥� student-teaching experiences.
The seven sites in the project also hire a teacher-in-residence who helps teach introductory physics and education methods courses.
The group will be vital for making changes, says Mr. Hein, because physics teachers rarely have the chance to observe others and talk about the best way to teach. Many high schools have only one physics teacher, and sometimes that teacher is responsible for teaching other sciences as well.
鈥淎 lot of efforts are being made to get this research out there,鈥� added Mr. Stein of the American Physical Society. But he said 鈥渋t鈥檚 hard鈥� to change how teachers teach.
Coverage of research is underwritten in part by a grant from the Spencer Foundation.
