2005年10月12日,“神舟六号”飞船顺利升空后,在离地面340km的圆轨道上

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问题:

2005年10月12日,“神舟六号”飞船顺利升空后,在离地面340km的圆轨道上运行了73圈.运行中需要多次进行“轨道维持”.所谓“轨道维持”就是通过控制飞船上发动机的点火时间、推力的大小和方向,使飞船能保持在预定轨道上稳定运行.如果不进行轨道维持,由于飞船在轨道上运动受摩擦阻力的作用,轨道高度会逐渐缓慢降低,在这种情况下,下列说法正确的是(  )

A.飞船受到的万有引力逐渐增大、线速度逐渐减小

B.飞船的向心加速度逐渐增大、周期逐渐减小、线速度和角速度都逐渐增大

C.飞船的动能、重力势能和机械能都逐渐减小

D.重力势能逐渐减小,动能逐渐增大,机械能逐渐减小

考点:人造地球卫星万有引力定律的其他应用
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A teenage girl couldn't stand(忍受) her family rules,so she left home.
  She wanted to be a star and became   1 . But she had a little education and  a few years later,she had to ask for food on the street for a living. Now her father has  2  . Her mother is an old woman. But she is still     3  her daughter. She went to every corner of the city. Everywhere she goes,she put up a big photo of herself on the wall. At the lower part of the    4  she writes,“I still love you …Come back home!”
One day,the daughter saw one of the photos. She was so surprised that she couldn't believe her    5  . “Is that my mother?”She moved    6 and read the words,“I still love you…” She cried. When she got home,it was early morning. She pushed the door. The door    7   itself. She rushed to the bedroom at once. Her mother was sleeping there. She woke her mother up,“It's me!Your daughter is back home!”The mother and daughter looked at each other excitedly,full of   8   tears. The daughter asked,“     9  is the door unlocked?A thief could get in.” The mother answered softly,“The door    10 locked  after you left. We miss you all the time. We believe that you'll come back some day.”
The door of parents’ love for their children will never be closed.
小题1:
A.famousB.poorC.prettyD.polite
小题2:
A.lostB.diedC.worriedD.changed
小题3:
A.looking upB.looking atC.looking forD.looking down
小题4:
A.wallB.photoC.house D.door
小题5:
A.earsB.noseC.headD.eyes
小题6:
A.fartherB.closerC.betterD.cleaner
小题7:
A.opened B.brokeC.closedD.locked
小题8:
A.sorryB.wonderfulC.sadD.happy
小题9:
A.When B.WhyC.WhereD.Which
小题10:
A.neverB.alwaysC.sometimesD.often
题型:多选题

如下图是跳水运动员跳板跳水时的情景,从运动员腾空跳起向上运动后再向下落入水中,若不计空气阻力,则在整个过程中:

[ ]

A、运动员的动能一直增大,机械能不变

B.运动员的重力势能一直减小,机械能减小

C.运动员的动能先减小后增大,机械能不变

D.运动员的重力势能先减小后增大,机械能增大

题型:多选题

两性沟通的五大目的,是什么?

题型:多选题

设有关系R、S分别如表6-4和表6-5所示,则关系代数表达式R÷S的结果集为______。

表6-4 关系R
A B C
a1 b1 c1
al b2 c1
a2 b2 c2
表6-5 关系S
B D
b1 d1
b2 d1

A.

B.

C.

D.

题型:多选题

“民为贵,社稷次之,君为轻”这一思想的提出者是()。

A.孔子

B.孟子

C.庄子

D.老子

E.荀子

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