摘要或動機

在網路上看到甩毛巾、皮鞭的影片，會產生巨大的聲響，查找了資料，我們知道當發聲體超過音速時便會產生音爆。部分文獻提到，毛巾或皮鞭生成音爆原因是來自於角動量守衡理論，我們想利用實驗方法來驗證其正確性，因此利用video point 來分析影片討論手的加速度和毛巾末端質量、長度的關係，並用crocodile physics 做電腦模擬，我們發現毛巾長度與音爆產生無關，這樣和角動量理論模型有所不同。所以我們嘗試利用能量守恆及自由端反射駐波理論來解釋毛巾產生音爆關係，並利用影片分析及crocodile physics 驗證其正確性。We saw the film clippings on the Internet about snapping towels and whips, which made a big noise. After going through related literature, we found out that it is called the sonic boom .Some papers say that the sonic boom results from the Location momentum conservation theory. To prove its accuracy, we used a kind of computer software called Video Point to analyze in the clippings the movement of the hand, understanding the relationship between the mass of the towel end and the length of the towel. We also used another software called Crocodile Physics to simulate the whole process. We discovered that there is no connection between the length of the towel and the sonic boom. It does not conform to the Location momentum conservation theory. We then in turn employed energy conservation theory and the trait of the standing wave (specific wave length) to explain, when we also used Video Point and Crocodile Physics to prove.