盪鞦韆的奧秘與技巧

Conceptual Explanation of the Physics Principles and Tricks of Swings

江長屹(Chang-Yi Jiang)

《物理教育學刊》 17卷2期 (2016/12) Pp. 25-31

https://doi.org/10.6212/CPE.2016.1702.03

摘要

理解物理原理的內涵與應用，可以透過生活化實例來達成。好玩的盪鞦韆，其背後的物理原理並不簡單。本文從「功能原理」，先透過系統取定、力圖分析，再探討所有可能作功的力，以釐清盪鞦韆的奧秘。本文探討的鞦韆，侷限於硬式鐵條，但人的姿勢則包含站姿與坐姿兩種。首先，取定[人+椅子]為系統，則重力、摩擦力、正向力三者皆不作功，而空氣阻力會作負功，唯一能夠作正功的力只有張力，為了使張力作正功，人擺盪時的姿勢變化也有玄機。

關鍵字

盪鞦韆 ； 功能原理 ； 概念推理

並列摘要

Understanding the conceptions and applications of physics principles can be obtained through exploring the mysteries of everyday life examples. Playing on a swing may be simple, but the physics principles underlying it are profound. This paper analyzes the physics principles based on the Work-Energy Theorem selection of valid systems, and force diagram analysis to clarify the mystery of swings. Both of the standing up and sitting postures on hard rope swings are discussed. This paper reveals that only work done by the tension of the ropes can do positive work to the swing, and tricks for successfully playing on swings are also discussed.

並列關鍵字

swing ； work-energy theorem ； conceptual explanation