阅读段落

　　A simple analogy can help us to understand how a rocket operates. It is much like a machine gun mounted on the rear of a boat. In reaction to the backward discharge of bullets, the gun, and hence the boat, move forwards. A rocket motor’s ‘bullets’ are minute, high-speed particles produced by burning propellants in a suitable chamber. The reaction to the ejection of these small particles causes the rocket to move forwards. There is evidence that the reaction principle was applied practically well before the rocket was invented. In his Noctes Atticae or Greek Nights, Aulus Genllius describes ‘the pigeon of Archytas’, an invention dating back to about 360 B.C. Cylindrical in shape, made of wood, and hanging from string, it was moved to and fro by steam blowing out from small exhaust ports at either end. The reaction to the discharging steam provided the bird with motive power.

　　段落大意

　　本段介绍了火箭弹的工作原理以及该原理的起源。

　　阅读笔记

　　Operating principle：Like a machine gun mounted on the rear of a boat.

　　1. GUN: reaction to the backward discharge of bullets→the boat move forwards.

　　2. ROCKET:

　　a. ‘bullets’ are minute, high-speed particles produced by burning propellants in a suitable chamber.

　　b. reaction to the ejection of small particles→rocket to move forwards.

　　Origin of the principle:

　　360 BC, an invention, “the pigeon of Archytas” – it was moved to and fro by steam blowing out from small exhaust ports at either end.

　　逻辑关系

　　1. 比较(无逻辑连接词)

　　in reaction to the backward discharge of bullets, the gun, and hence the boat, move forwards

　　the reaction to the ejection of these small particles causes the rocket to move forwards

　　it was moved to and fro by steam blowing out from small exhaust ports at either end

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