自由落體實驗的歷史回顧與教學省思

學過高中物理的學生，真正知道自由落體實驗之物理意義的人數是寥寥可數的。絕大多數學生只記得「同時落地」這個答案，他們不知道故事中的伽利略爬上比薩斜塔「應該」丟的是哪兩樣東西，也不清楚伽利略作這個實驗到底是想證明什麼，或證明了什麼。從科學史的回顧，包括伽利略之前與之後的幾個自由落體實驗，一方面可以見到其實驗所拋下的兩物與實驗結果因示範者的理論背景而異，一方面則能更瞭解伽利略對自由落體的推理與論述，及其承先啟後之地位。在抽真空技術發展之後，自由落體實驗有了不同的展現面貌，例如十七世紀中波以耳抽真空進行的硬幣羽毛實驗、1971年太空人史考特在月球上做的鐵鎚羽毛實驗、以及2014年BBC在NASA的超大真空室拍攝保齡球和羽毛同時落下的影片。本文從自由落體實驗的歷史回顧，探討其對教學的啟發，以及這些演示實驗教學所引發的一些迷思，提供教學上的省思。

關鍵字

自由落體；伽利略；豬膀胱；重力加速度；真空；太空

並列摘要

The experiment at the Leaning Tower of Pisa is well-known to most people although no evidence proves whether Galileo ever performed it or not. When asked which objects Galileo dropped from the edge of the tower, to my surprise, most students thought the objects to be metal ball and cotton and they even misunderstood that the two objects would hit the ground at the same time. Most students were short of the logical reasoning ability when they heard the story. On the other hand, few physics teachers did understand students’ difficulties. They tend to emphasize Galileo’s rebuttal of Aristotle or the special situation such as the vacuum tube or the moon experiment. Consequently, the only thing students remembered was that these two objects ＂hit the ground at the same time＂ and they had no idea about which two objects had been dropped off and whether the two objects had the same weight or not. The way we see things is affected by what we know or what we believe. Looking back at history, before and after Galileo, there were many free fall experiments and their answers to which object reached the ground first depended on the concept of the demonstrators. History review helps us understand Galileo’s ratiocination and how he builds on the past and prepares for the future. Afterwards, Boyle’s technology of vacuum pumps has changed the face of the free fall experiments, such as Boyle’s vacuum tube of coin and feather, the Apollo 15 astronaut David Scott’s of dropping the hammer and the feather on the moon, and the free-fall bowling and some feathers in NSTA’s vacuum chamber in a BBC film. Based on these history reviews, several pedagogical reflections and implications can be drawn from this study.

並列關鍵字

free fall ； Galileo ； acceleration ； inflated bladder ； vacuum

國際替代計量

自由落體實驗的歷史回顧與教學省思

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