为了实验“神舟六号”飞船安全着陆,在飞船距离地面约1m时(即将着陆前的瞬间),安

题型:问答题

问题:

为了实验“神舟六号”飞船安全着陆,在飞船距离地面约1m时(即将着陆前的瞬间),安装在返回舱底部的四台发动机同时点火工作,使返回舱的速度由8m/s降至2m/s.设返回舱质量为3.5×103kg,减速时间为0.2s.设上述减速过程为匀变速直线运动,试回答和计算下列问题:(g取10m/s2

(1)在返回舱减速下降过程中,航天员处于超重还是失重状态?计算在减速时间内,航天员承受的载荷值(即航天员所受的支持力与自身重力的比值);

(2)计算在减速过程中,返回舱受到四台发动机推力的大小.

考点:人造地球卫星万有引力定律的其他应用动量定理
题型:问答题

引起非淋菌性 * * 炎最常见的病原体是()

A.解脲脲原体

B.沙眼衣原体

C.性病淋巴肉芽肿衣原体

D.杜克雷嗜血杆菌

E.白假丝酵母菌

题型:问答题

磺胺类药的抗菌机制是

A.抑制细菌二氢叶酸合成酶

B.抑制细菌二氢叶酸还原酶

C.改变细菌细胞膜通透性

D.破坏细菌细胞壁

E.影响细菌DNA回旋酶

题型:问答题

下列实验室项目中,哪项对SARS的诊断意义最小()

A.外周血淋巴细胞计数

B.SARS冠状病毒特异性抗体检测

C.RT-PCR检测SARS-CoVRNA

D.细胞培养

E.血清球蛋白

题型:问答题

Have you ever seen any students whose trousers hang so low that you can see their underwear? What do you think of that? Fashionable? Some of today’s teenagers are big fans of such a look. But recently this trend has been at the center of an argument in Italian middle schools. The headmaster of a school in central Italy has asked students to stop wearing low-rise jeans that expose underwear and parts of the body. His request came after a class trip, when he saw one boy's baggy trousers slide to his feet. He pointed out that this way of dressing is not suitable for school. But in Italy, a nation that takes fashion very seriously, the suggestion caused a debate among parents, teachers and students. The issue is whether the headmaster's request will limit students' freedom— or whether dress in Italian schools is too casual. A parents' group praised the move in favor of good taste, while others advised schools to stop worrying about fashion and fix up old school buildings. “We do not want to kick fashion out,” the headmaster explained, “but extremes of fashion like this are not right in school.” Many other schools have now requested that their students also stop wearing such trousers. Most students have simply ignored the request. Ludovica Gaudio, 14, wore extremely low trousers exposing orange underwear in class. It was cold, so she wore a matching orange scarf. Another 14-year-old said she would probably respect the request, simply for practical reasons. “I don't really feel comfortable in those sort of jeans,” said Sarah Lattanzi, “in winter, when dressed like that, it's quite cold and I am afraid my stomach will ache.”

小题1:What led to the argument in Italian middle schools?______

A.Students' craze for fashions.

B.Clothes that are too exposing.

C.Students' ignoring dress codes.(规则)

D.Students' underwear.小题2:Which of the following supports the headmaster's request?___

A.Fashion should be taken seriously.

B.Fashion should not be followed in school.

C.Students should have their freedom in choosing what they wear.

D.Students should be encouraged to have good taste in clothes.小题3: The argument against the headmaster's request is that ______.

A.dress in Italian schools is too casual

B.fashion should not be followed in school

C.schools should pay attention to things more important than students' clothes

D.low-rise jeans can do harm to youngster's health小题4:The purpose of this story is to ________

A.show Chinese students that wearing very fashionable clothes in school is under attack in other countries, too.

B.show that dress code is necessary even in a country like Italy

C.let us see that Italian students react differently to schools' requests.

D.tell us that a debate started in Italian middle schools over the way students dress in School

题型:问答题

由于现场施工劳动的特点,劳动力结构应具有的特点包括()。

A.长工期少,短工期多

B.技术工少,普通工多

C.老年工人少,中青年工人多

D.工资较少,劳动力度强

E.女性工人少,男性工人多

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