探討國中三年級學生對於重力概念之瞭解及心智模式

Abstract

本研究的主要目的是以重力為例，以三角交叉檢視（triangulation）的方式，使用二階段式設計及臨床晤談等方法，以不同面向探討學生對於力的初始概念、對非接觸力概念的瞭解，並診斷學生對重力另有概念的種類和認知架構，以及學生對詮釋重力概念的心智模式。研究的樣本為國中三年級學生共337人，其中男生181人，女生157人，受測學校分佈的地區為台北縣市共七所公立國中。 發現學生對於重力有一些另有概念的看法，例如：「蘋果和地面之間有空氣存在，蘋果才能掉下來」、「月球和地球之間有一排斥力，此力和地球引力平衡」、「月球在地球的大氣層外，不受地球引力的影響」、「月球因為沒有空氣，所以在月球上的物體或太空人均不會掉落或跌落至月球表面」、「地球會繞著太陽運行，是因為其他星球對地球的拉力達到平衡」等。 本研究分析之國三學生對於重力現象詮釋的心智模式歸納後有四種類別：（一）經驗論模式：他們認為非接觸力作用需要靠介質的傳遞，地球引力僅能存在大氣層內，在月球上因缺少空氣，所以沒有引力，因而月球表面上的物體會任意的飄浮。天體的運行乃是宇宙形成時，具有的自然現象。（二）大氣壓力論模式：學生認為非接觸力是要靠介質傳遞的，但是如果有大氣壓力，則物體不但會受到地球引力的作用，也會因為大氣壓力的作用而具有重量。（三）引力製造論模式：認為引力是星球本身製造出來的，若是製造出來的引力大，則物體所受的引力較大。物體在月球所受的引力較小，是因為月球本身所儲存的能量不足，製造的引力較小的緣故。（四）準科學平衡論模式：學生對於非接觸力的作用具備有較完整的基本科學概念，對於地球環境及月球環境下的事例亦能用基本的科學概念來詮釋現象，延伸至天體運動時，學生會在認知架構中試圖利用靜力平衡的概念來詮釋。

The aim of this research is to take gravity as an example, using the method of clinical interview and the two-tier design, triangulating from different dimensions students’ understanding about force and action-at-distance, and diagnosing students’ alternative conceptions about gravity and their mental models of gravity. The sample population is 338 in total, 181 male and 157 female of Ninth-grade Students, from seven public junior high schools in Taipei City and County. Students have alternative conceptions about gravity; for instance, there exists air between the apple and the ground, so the apple can drop down, and there is an counterforce between the earth and the moon; the counterforce is equal to gravity; the moon is outside the atmosphere of the earth, so it will not be affected by gravity; because there is no air on the moon, objects or astronauts will not drop down on the surface of the moon; the earth moves around the sun because the pulling force is balanced between the earth and the other planets. In this study, there are four categories of mental models, which Ninth-grade Students develop as concepts in interpreting gravity: I. Experientialism: students think that action-at-distance works only through medium for transmission. Gravity is confined in the atmosphere, there is no gravity on the moon because no air is there. So, any object can float above the surface of the moon. The orbit of a planet is a natural phenomena, which has been formed since the universe was created. II. Atmospheric pressure: Students think that action-at-distance is transmitted through medium, but if there is atmosphere, objects will be attracted by gravity and have weight because of the atmospheric pressure. III. Generation of gravity: Students think that gravity is generated by a planet itself. And the greater the generated gravity is, the weightier an object on it will be. An object on the moon is lighter than on the earth because the moon has stored less energy, which also generates less gravity than the Earth. IV Quasi-scientific balance: Students have a comparatively better scientific concept about action-at-distance and can apply some fundamental concepts to interpret the phenomena formed under the circumstances of the Earth and the moon; when students further apply them to the orbit of a planet, they interpret it according to their concept about the balance of static force.