In recent years teaching strategies which emphasize that students must construct their own knowledge have been introduced. These approaches have some common components. First, they involve some preliminary phase in which the students are engaged actively in hands-on experiences. These experiences are designed to bring into the open some of the students' preconceptions and enable the students to explore ideas related to the topics under discussion. These activities provide a means by which the students can express their own ideas about the physical world and by which the teacher can learn about the students’ preexisting understanding of nature and build upon them.

Another phase involves the introduction of new (to the students) physical principles. In some of the models of instruction these principles are introduced by the instructor who builds on the previous experiences of the students. In other models the students are guided to discover these principles by further discussion and experimentation. The difference between the two approaches is frequently the amount of time which the instructor is willing to devote to this stage of learning. Clearly, the guided discovery method will take longer than a teacher-centered introduction of new material.

Also common to all of these models is an immediate application of the newly introduced or discovered principles. The students are challenged to apply these principles in an environment where they are completing hands-on experiments. Usually, the student completes a number of experiments and then uses the newly learned principles to explain the experimental results and to generalize to other situations.

Several years ago I applied these ideas about learning to a large class, over 100 students. I did have some assistance -- ranging from undergraduate, who sometimes did not know any physics and did only clerical work, to first year graduate students who knew some physics but only knew the lecture way of learning because that was the only one they had seen. The assistance was not enough help to break the class into several smaller classes. I wanted the course to be student-centered. How could I create a student-centered environment with these limitations? The answer lay in shifting some of the responsibility for learning to the students through self-paced activities and in using technology.

My students start each cycle of learning with "self-paced" explorations. I put self-paced in quotation marks because they schedule their own time to complete the exploration, but they have a deadline. The explorations are available after class on Monday and must be completed before class on Wednesday. These activities are several experiments which the students must complete and record their observation. The students are not looking for "right" answers; they are just experimenting and observing. Then, on Wednesday the whole group meets to discuss the explorations and learn a new concept. As I begin to introduce a new concept, I ask "Tell me what you learned? What did you observe from the explorations?"

Because they have all had the same experiences before class, they discuss the activities even though we are meeting in a room that holds 100 people. After the discussion and the introduction of new concepts we move on to a "self-paced" application which is due before class on Friday. This application is graded more carefully than the exploration because we want to provide feedback on how well they are applying the concept that they just learned. On Friday, we come back together as a large class. This class always starts with questions about the application. By watching the students complete the application, I compose questions in case nobody else has one. When we have completed this discussion, we summarize the week and start the next cycle.

I have used this approach for 17 or 18 years. My colleagues ask "How can you teach the same class that many times?" When you listen to the students and respond to their needs, it is not the same class; it's never the same as the previous year. Somebody always comes up with a different idea or approach that teaches me something new about how students learn or about physics. Then, the class goes in a direction that it has not gone before.

In selecting activities I keep in mind that the students live in a real world. Students have never seen frictionless planes, point masses, massless pulleys, or adiabatic processes. When we use these concepts in a class, we still separate the real world from the physics of the classroom. While a model, such as the ones described above, is a vast improvement over the lecture approach to undergraduate physics teaching, it loses some of its impact when we discuss only idealized, laboratory situations.

Fortunately, with the advent of modern technology we can easily bring analysis of real world situations into the classroom. While several technologies can be used to provide experiences with real world data, I have found video to the most useful. Of course, students see many special effects on video and, thus, are not likely to believe everything that we present in this format. Thus, important learning strategies are to have students record their own video or collect measurements from existing video. The interactive videodisc provides a convenient method for collecting data from existing video. By marking on the screen or a transparent plastic covering the screen, they can collect data about distance and time. From these data they may analyze a variety of motions. More advanced techniques in modeling of events can also be completed through this method of analysis.

We have developed more sophisticated method of collecting data using video. Developments in digitized video with computers allow students to capture their own experiments and analyze them with a variety of software tools. The use of data collection from video scenes helps our students see the connections between events which they recorded and abstract models of the physical world.

Finally, our learning and teaching strategies must reflect our concern for how different groups of students learn. Many students who are capable of advanced study in physics have found the general approach to teaching and learning physics not acceptable. Further physics and other sciences seem to be less attractive to females and minorities than to white males. In general, by looking at the numbers and types of people who find physics interesting, we can conclude that we need to examine our teaching methods, The strategies described here break the mold of how physics is taught and learned. I hope that they can help all members of the undergraduate population see that science and technology can be interesting and, even, exciting.