我国数据中继卫星定点在东经77°上空的同步轨道上，对该卫星下列_爱下问搜题

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问题多选题

我国数据中继卫星定点在东经77°上空的同步轨道上，对该卫星下列说法正确的是（　　）

A．加速度比静止在赤道上物体的加速度小

B．离地面高度一定

C．在赤道的正上方

D．运行速度大于第一宇宙速度

答案

A、中继卫星与地球自转的周期相同，根据a=r(

2π

T

)2知，卫星的加速度大于静止在赤道上物体的加速度．故A错误．

B、根据万有引力提供向心力知，G

Mm

r2

=mr(

2π

T

)2，周期一定，则轨道半径一定，卫星离地的高度一定．故B正确．

C、同步卫星轨道在赤道的正上方．故C正确．

D、根据万有引力提供向心力得，G

Mm

r2

=m

v2

r

，v=

GM

r

，轨道半径越小，线速度越大，第一宇宙速度的轨道半径等于地球的半径，所以卫星的运行速度小于第一宇宙速度．故D错误．

故选BC．

完形填空

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单项选择题

以下疾病在闪光ERG检查中均表现为a波与b波都下降，除外（）

A.视网膜中央动脉或静脉阻塞

B.视网膜色素变性

C.玻璃体积血

D.视网膜脱离

E.脉络膜视网膜炎