神舟十号飞船于2013年6月11日顺利发射升空，它是中国“神舟”号_爱下问搜题

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问题选择题

神舟十号飞船于2013年6月11日顺利发射升空，它是中国“神舟”号系列飞船之一，是中国第五艘搭载太空人的飞船。升空后和目标飞行器天宫一号对接。任务是对“神九”载人交会对接技术的“拾遗补缺”。已知神舟十号飞船的发射初始轨道为近地点200 km、远地点330 km的椭圆轨道，对接轨道是距地表343 km的圆轨道。下列关于神舟十号飞船的说法中错误的是

A．发射速度必须大于7.9 km/s

B．在对接轨道上运行速度小于7.9 km/s

C．在初始轨道上的近地点速度大于在远地点的速度

D．在初始轨道上的周期大于在对接轨道上的周期

答案

答案：D

题目分析：第一宇宙速度是环绕地球运动的最大速度，发射的最小速度，因此神舟十号飞船发射速度必须大于7.9 km/s，选项A正确；同理在对接轨道上运行速度小于7.9 km/s，选项B正确；从远地点运动到近地点，由于万有引力做正功，因此在初始轨道上的近地点速度大于在远地点的速度，选项C正确；由周期公式可知半径越大周期越大，选项D错误；故选D

点评：本题难度较小，熟悉第一宇宙速度定义、熟练掌握周期公式是关键

单项选择题

High school dropouts earn an average of $9,000 less per year than graduates. Now a new study dispels a common belief why they quit. It’s much more basic than flunking out.
Society tends to think of high school dropouts as kids who just can’t cut it. They are lazy, and perhaps not too bright. So researchers were surprised when they asked more than 450 kids who quit school about why they left.
"The vast majority actually had passing grades and they were confident that they could have graduated from high school. " John Bridgeland, the executive researcher said. About 1million teens leave school each year. Only about half of African American and Hispanic student will receive a diploma, and actually all dropouts come to regret their decision. So, if failing grades don’t explain why these kids quit, what does Again, John Bridgeland: "The most dependable finding was that they were bored. " "They found classes uninteresting; they weren’t inspired or motivated. They didn’t see any direct connection between what they were learning in the classroom to their own lives, or to their career aspirations. "
The study found that most teens who do drop out wait until they turn sixteen, which happens to be the age at which most states allow students to quit. In the US, only one state, New Mexico, has a law requiring teenagers to stay in high school until they graduate. Only four states: California, Tennessee, Texas and Utah, plus the District of Columbia, require school attendance until age 18, no exceptions, another researcher, says raising the compulsory attendance age may be one way to keep more kids in school.
"As these dropouts look hack, they realize they’ve made a mistake. And anything that sort of gives these people an extra push to stick it out and it through to the end, is probably helpful measure. "
New Hampshire may be the next state to raise its school attendance age to 18. But critics say that forcing the students unwilling to continue their studies to stay in school misses the point—the need for reform. It’s been called for to reinvent high school education to make it more challenging and relevant, and to ensure that kids who do stick it out receive a diploma that actually means something.

In the last paragraph, the writer is trying to ______.

A．analyze the reason why students quit school
B．suggest raising the compulsory attendance age
C．raise awareness of reforming high school education
D．wish to make laws to guarantee no education

问答题论述题

指出我国10大道地药材的区域范围，并各列举3种道地药材。