engleski

Probing students' conceptual knowledge of satellite motion by use of diagrams

Regardless of nowadays widespread use of satellites in navigation, communication and earth observation, they are still often considered as “mysterious” objects, mostly because they travel in space where most of us have never been, so that developing an intuitive understanding of satellite motion remains out of our scope. That's probably why the dynamics of orbital motion, although being central to proper understanding of many aspects of physics, proved to be conceptually difficult for students. Being aware of conceptual difficulties of this kind, Newton wrote a popular text to explain the orbital motion of the Moon, that was published a year after his death. In this paper he demonstrated the significance of the velocity of the satellite as equally responsible for the orbital motion as the attractive gravitational force of the Earth [1]. Besides, the gravitational force is directed to the center of the Earth so that the center of the circular satellite orbit and the center of Earth should match. In this paper we present students’ ideas about these important issues. For this purpose, we surveyed 276 high-school and university students from Croatia. Students were presented a nontraditional problem [2] with a diagram of the motion of the Earth satellite in different orbits and were asked to choose the one which is the best to receive satellite TV channels in Croatia. Implicitly students were expected to recognize the only possible orbit, for which the gravitational force is directed toward the center. The students were also asked several questions to explain their choice. In order to gain insight into teachers' awareness of student's knowledge, we asked 48 physics teachers to predict how their students would answer the given problems. The results of our study suggest that most students have difficulties with providing physically based explanations. They tend to use phenomenological primitives [3]. Specifically, they tend to use the “closer is stronger” p-prim when attempting to identify the satellite orbit which would ensure the receipt of satellite television signal at a certain location, paying no attention to the direction of the gravitational force. Our results also show that students across different educational levels and curricula in Croatia lack deep understanding and functional knowledge related to the concepts of circular motion, gravitational force and first cosmic velocity. This conclusion is supported by the fact that only 4 % of students provided complete answers regarding the causes of satellite’s motion. Moreover, the teachers considerably overestimate students’ abilities. Based on this study we believe that the use of diagrams could facilitate designing an interactive classroom environment, especially when it comes to promoting of a creative classroom discussion. However, further experimental studies are necessary in order to additionally reinforce the effectiveness of the proposed approach.</br> References:</br> [1] I. Newton, A treatise of the system of the world (printed for F. Fayram, London, 1731).</br> [2] A. A. DiSessa, Cogn. Instr. 10 (1993) 105. </br> [3] N. Erceg, I. Aviani and V. Mešić, Can. J. Phys. 92 (2014) 9.

gibanje satelita

nije evidentirano