题干

某汽车以10m/s的速度行驶,驾驶员发现正前方70m处有一辆与汽车同方向行驶的自行车,正以4m/s的速度匀速行驶,驾驶员以﹣0.25m/s2的加速度开始刹车,停下前是否发生车祸?判断并写出运算过程.

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答案(点此获取答案解析)

解:汽车速度减小到4 m/s所需的时间t= 100.25
4
s=24 s
在这段时间里,汽车、自行车行驶的距离
汽车:x1=v0t+

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    Have you ever seen any students whose trousers hang so low you can see their underwear? What do you think of that? Fashionable? Some of today's teenagers are big fans of such a look.____.

    The headmaster of a school in central Italy has asked students to stop wearing low-rise jeans that expose underwear and part of the body. His request came after a class trip. One day, he saw one boy's baggy trousers slide to his feet ____.

    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.

    ____ “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.

    ____ Ludovica Gaudio, 14, wore extremely low trousers exposing orange underwear in class. It was cold, so she wore a matching orange scarf. ____ “I don't really feel comfortable in those sorts of jeans,” said Sarah Lattanzi, “in winter, when dressed like that, it's quite cold and I am afraid my stomach will ache.”

A. But recently this trend has been at the center of an argument in Italian middle schools.

B. 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.

C. He pointed out that this way of dressing is not suitable for school.

D. Most students have simply ignored the request.

E. Another 14-year-old said she would probably respect the request, simply for practical reasons.

F. Requests.

G. Schools should pay attention to things more important than students' clothes.