精品一区二区免费在线观看_国产精品久久久久久av福利软件_97成人精品区在线播放_国内成人精品一区

The rockets take astronauts and man-made satellites into space. The satellites are used for communication, weather monitoring and research. But how do satellites stay up without falling down?
There are two opposite forces (力量) acting on the satellite. One of them is the force of gravitation (地心引力), which tries to pull the satellite towards the earth. The other force is created by the rotation (旋轉) of the satellite around the earth. This force tries to take the satellite away from the earth. With these two forces, the satellite goes round and round. The gravitational pull of the earth (the force which pulls everything towards the ground) is like a rope which keeps the satellite from flying away.
Everything that goes up has to come down. It is only a matter of time before a satellite comes back to the earth. As time goes by, the satellite loses its speed, which makes the gravitational pull stronger than the force pulling it away. This makes the satellite crash (墜落) down to the earth.
【小題1】Which of the following uses of satellites is NOT mentioned?

根據漢語意思，完成下列句子。（每小題2分，共5小題，計10分）
【小題1】你給我這么多幫助，你真好。
               to give me so much help.
【小題2】大部分時間我們都在一起；因此我們從不覺得寂寞。
We are together most of the time, so we              
【小題3】珍愛自己，遠離不健康的書。
Take good care of yourself and              bad books.
【小題4】近五年來在西昌已發射了幾顆人造衛星。
Several man-made satellites             in Xichang in the past five years.
【小題5】我認為自己想辦法要比仿照別人的樣子要好。
I think it’s better to find our own way than             .  

_________ the help of man-made satellites, we can know what the weather will be like

in the next few days.