The rockets take astronauts and man﹣made satellites（卫星）into space． The satellites are used for communication， weather checking and research．But how do satellites stay up without falling down？

    There are two opposite forces influencing the satellite． One of them is the force of gravitation（地心引力） ， which tries to pull the satellite towards the earth and is like a rope which keeps the satellite from flying away．The other force is created by the turning 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．

    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 force pulling it towards the earth stronger than the force pulling it away． This makes the satellite fall down to the earth．

判断文章后面的问题，正确的答案写T，错误的答案写F．

（1）Two same forces have an influence on the satellite．　　

（2）The force created by the turning keeps the satellite from flying away．　　

（3）Two opposite forces make the satellite turn round and round．　　

（4）The satellite will stay in space forever．　　

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