问题 选择题

中国南方航空公司某架客机安全准时降落在规定跑道上,假设该客机停止运动之前在跑道上一直做匀减速直线运动,客机在跑道上滑行距离为s,从降落跑道上到停下所需时间为t,由此可知客机降落时的速度为( )

A.s/t

B.s/2t

C.2s/t

D.条件不足,无法确定

答案

答案:C

题目分析:由平均速度公式可得:而平均速度汽车的末速度为零,则下降时的初速度,故选C.

点评:变速直线运动的平均速度等于中间时刻的速度,这一规律在解题时一定要做到熟练应用.

阅读理解

You may feel curious about students in other countries: Do they also have so much homework? What do they do in their free time? On April 8, a report came out on the lives of school students in China, Japan, South Korea and the US. It surveyed around 6,200 students from the four countries last year. You will find the answers to many of your questions in this report.

Who studies hardest?

Chinese students spend the most time studying. Nearly half of Chinese students spend more

than two hours on their homework every day. That’s much more than students of the US (26.4%), Japan (8.2%) and South Korea (5.2%).

Who sleeps most often in class?

Japanese students fall asleep in class most often. About 45% of them say they sometimes doze off in class. In South Korea, it’s 32%; in the US, 21%; and 5% in China.

South Korean students don’t like taking notes. About 70% say they write down what the teacher says in class, many fewer than in Japan (93%), China (90%) and the US (89%).

What do they do after school?

In their free time, most Chinese students study or surf the Internet. Most American students hang out with their friends. Most Japanese students do physical exercises. Most Korean students watch TV.

小题1:How many countries were surveyed in this passage?

A.Two

B.Three

C.Four

D.Five小题2:Who studies hardest?

A.Chinese students.

B.Japanese students.

C.South Korean students.

D.American students.小题3:Who sleeps least often in class according to the report?

A.Chinese students.

B.South Korean students.

C.American students.

D.Japanese students.小题4:How many South Korean students write down what the teacher says in class?

A.93%.

B.90%.

C.89%.

D.70%.小题5:According to the passage, we know          .

A.Japanese students spend the most time studying

B.Japanese students fall asleep in class most often

C.Japanese students don’t like taking notes

D.most Chinese students watch TV in their free time

单项选择题