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III. DEVELOPMENT AND ASSESSMENT
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III. DEVELOPMENT AND ASSESSMENT
OF CURRICULUM These examples illustrate some specific difficulties that teachers often share with many university students. Because of their responsibility to help their students learn, the situa- tion for teachers is more serious and needs more attention. They must know and be able to do more than is expected of their students. We should therefore ask what we want young students to know and be able to do and prepare teachers accordingly. These questions have led to the development of Physics by Inquiry (PbI), a laboratory-based curriculum pri- marily intended for the preparation of preservice and inser- vice teachers but also suitable for other populations. 13,14 We begin instruction on all topics by drawing on research that identifies where students are intellectually. We use this information to design, test, and revise curriculum on the ba- sis of experience in classes at UW and at pilot sites. Teaching is by asking questions to help students construct a coherent conceptual framework, rather than by telling. The emphasis is not on solving standard problems, but on developing the reasoning ability needed to apply relevant concepts to situa- tions that have not been memorized. The curriculum explic- itly addresses specific difficulties that research has shown may preclude a functional understanding. Even when teach- ers do not have these difficulties themselves, it is likely that their students will. PbI helps teachers develop the type of knowledge necessary to be able to teach a given topic effec- Fig. 1. Question about balancing. Students are told that the bat, which has uniform density, remains at rest when placed on a finger as shown. They are asked whether the mass to the left of the balance point P is greater than, less than, or equal to the mass to the right of the balance point. Fig. 2. Question about acceleration. Students are shown the diagram of a ball rolling first up and then down the ramp. They are asked to draw vectors for the velocity and the acceleration at each of the marked points. Fig. 3. Question about electric circuits. Students are told the bulbs are iden- tical and the batteries are identical and ideal. They are asked to rank the bulbs from brightest to dimmest. 764 764 Am. J. Phys., Vol. 74, No. 9, September 2006 McDermott et al. Teacher Education in Physics 149 tively 共pedagogical content knowledge兲. 15 Ongoing assess- ment that includes pretests and post-tests is an integral part of the iterative process involved in our ongoing curriculum development. We illustrate our design and assessment of cur- riculum in the context of dynamics. Design of curriculum. Student understanding of dynamics has been the focus of much research by our group and others. 7,10 The results have guided the development of Dy- namics. This module builds directly on Kinematics, in which the concepts of velocity and acceleration are developed from their operational definitions. Dynamics begins with the con- cept of force as a push or a pull. As in all of PbI, the equip- ment is simple and inexpensive so that it is readily accessible to teachers. Measurement procedures are as straightforward as possible with no black boxes. We start with simple “pull meters” made of rubber bands and meter sticks, rather than with spring scales or force probes. Students build and cali- brate the pull meters and explore how multiple pulls affect the motion of a wheeled cart. They find that a cart subject to a constant pull undergoes constant acceleration. Experiments with wooden blocks on rough surfaces and pieces of dry ice on level slate surfaces lead students to rec- ognize that an interaction between surfaces can be thought of in terms of a force. These experiments help students distin- guish between a single applied force, for example, exerted by a pull meter or a hand, and the net force that an object ex- periences. The students build on their previous experience with kinematics and explore cases in which the net force is exerted in the direction of motion and in the opposite direc- tion. They conclude that an object accelerates in the direction of the net force. The well-known tendency to associate force and velocity is explicitly addressed. For example, the stu- dents consider hypothetical dialogues in which fictional stu- dents express common incorrect ideas. The students use spring scales 共calibrated in newtons兲 to conduct experiments on carts to which varying numbers of identical objects have been added. They find that the net force required to produce a given acceleration increases as the number of objects increases. They are then led to develop the concept of inertial mass and arrive at an algebraic expres- sion of Newton’s second law. Subsequently, the students ex- plore gravitational and frictional forces in more detail. They also develop skill in drawing free-body diagrams. Newton’s third law is introduced by experiments in which students find that two magnets exert forces of equal magnitude and oppo- site direction on each other, regardless of which magnet is stronger. Subsequent experiments and exercises provide stu- dents with experience in applying Newton’s laws to systems of increasing complexity. There is an emphasis on the development of scientific rea- soning skills throughout Dynamics. The module stresses graphing, proportional reasoning, and vectors. Ideas intro- duced in the Kinematics module, for example, the interpre- tation of the slopes and the areas under the curves for graphs of position, velocity, and acceleration as functions of time, are reinforced. Thus, mathematics and physics teachers are given concrete ways to help students relate differentiation and integration to real-world phenomena. The process of scientific model building is made explicit. In particular, the difference between observation and infer- ence is stressed repeatedly. For example, students are ex- pected to recognize that the extension of a spring scale from which an object is hanging is not a direct measurement of the gravitational force exerted on the object; rather, it can be used in conjunction with Newton’s second law to deduce the magnitude of the force. Download 231.88 Kb. Do'stlaringiz bilan baham: |
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