问题 问答题

据报道,“9•11”事件后,美国为打击国际恐怖主义而对阿富汗实施军事打击,第一轮攻击是停泊在阿拉伯海的美国航空母舰“罗斯福”号上发射“战斧”式巡航导弹开始,第二轮攻击便是由航空母舰上战斗机实施空中打击.已知航空母舰上的战斗机起飞时的最大加速度是5.0m/s2,速度需50m/s才能起飞,现航空母舰甲板长度长160m.试问:

①飞机能安全起飞吗?说明理由.

②若不能安全起飞,为了使飞机能安全起飞,需要在航空母舰上安装助推器,让飞机在短时间△t=1.5s内立即达到一定速度,已知飞机质量为5.4t,忽略飞机在被助推期间所受阻力,求飞机受到的助推器的平均推力.(助推器装在160m跑道外,并使获得相应速度后才进入该跑道)

答案

(1)设飞机能够安全起飞的甲板长度为S,则:S=

vm2
2a1
=250m>s0=160m.

所以飞机不能安全起飞,飞机要安全起飞还需要一定的初速度v0    

(2)助推器弹射飞过程,根据牛顿第二定律得:F=ma2

根据速度时间公式得:v0=a2△t0         

起飞过程有:vm2-v02=2a1s0

联立解得:F=1.08×105N

答:①飞机不能安全起飞,飞机要安全起飞还需要一定的初速度v0

②飞机受到的助推器的平均推力为1.08×105N

阅读理解

阅读理解。

     It is really possible to be bored to death,scientists have found.Researchers say that

people who live a boring life are more likely to die young,and that those who experienced

"high levels" of boredom are at double risk (危险) of dying from heart disease or a stroke

than those who are satisfied with their life.

     Researchers studied the results of 7,524 people aged between 35 and 55 who were

interviewed between 1985 and 1988 about their levels of boredom.Of those 7,524 people

who were monitored (跟踪调查) over 25 years,those who said____________were nearly

40 percent more likely to have died by the end of the study than those who did not.

     The original survey found one in ten people had been bored within the past month,with

women more than twice as likely as men to suffer from boredom.Younger employees and

those with more boring jobs were also found to be more likely to suffer from boredom.

     Martin Shipley,who wrote the report,said,"People who are bored are more likely to turn to

unhealthy habits like drinking,smoking,taking drugs,and getting addicted to the Internet,which

can cut people's lifeexpectancy (寿命).It_is_important_that_people_who_have_dull_jobs

_find_outside_interests_to_keep_off_boredom,rather_than_turn_to_drinking_or_smoking."

     A scientist said those who are bored should try to be happier by thinking more about the

needs of others."From being all me,me,me,they should be thinking-what can I do for my

family,my friends,my colleagues,even my boss?" he said.

1.What's the main idea of the passage?(Please answer within 8 words.)

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2.Fill in the blank in Paragraph 2 with proper words.(Please answer within 5 words.)

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3.What does the original survey show about people?(Please answer within 15 words.)

________________________________________________________________________

________________________________________________________________________

4.Which sentence in the passage is the closest in meaning to the following one?

According to a scientist,people who feel bored should focus more on the needs of others in

order to be happier.

________________________________________________________________________

________________________________________________________________________

5.Translate the underlined sentence in Paragraph 4 into Chinese.

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判断题