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天宫一号目标飞行器经过多次变轨后进入预定轨道，若在变轨过程中的某一稳定轨道近似于圆形轨道，且离地高度为348km，则天宫一号在轨道上所需的向心力是由______提供的，其运行周期为______h．（地球质量M=5.98×1024kg，地球半径为6.4×106m，引力常数G=6.67×10-11Nm2kg-2）．

答案

天宫一号在轨道上做圆周运动靠地球的万有引力提供向心力．

有：G

Mm
(R+h)2
=m(R+h)(
2π
T
)2

解得T=

4π2(R+h)3
GM
=
4×3.142×(6.4×106+348×103)3
6.67×10-11×5.98×1024
s≈1.53h．

故答案为：地球的万有引力，1.53

阅读理解

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