雅思阅读辅导：火箭弹的工作原理　　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 motors 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 bulletsthe 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 particlesrocket 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 　　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