问题 填空题

飞机装满燃料后最多可以连续飞行6 h,在有风的情况下,可以确定飞机从基地出发连续飞行4 000 km再返回基地而不需加油.
(1)无风测试时,飞机的速度是1 350 km/h;
(2)此时,工厂烟囱里冒出的烟以150 km/h的速度飘散。

答案

参考答案:C

解析:

条件(1):v飞机=1 350 km/h.条件(2):v=150 km/h,综合条件(1)(2),顺风时v1=1 500 km/h,逆风时v2=1 200 km/h.从基地出发4 000 km然后返回所耗时间:t=

单项选择题
单项选择题

The worst thing about television and radio is that they entertain us, saving us the trouble of entertaining ourselves.

The main idea of this passage is that ______.
A. TV and radio can amuse us with beautiful songs and music
B. TV and radio prevent us from self-entertainment
C. people should sing songs and read books aloud themselves
D. parents should sing songs and read books aloud to their children

A hundred years ago, before all these devices were invented, if a person wanted to entertain himself with a song or a piece of music, he would have to do the singing himself or pick up a violin and play it. Now, all he has to do is turn on the radio or TV. As a result, singing and music have declined.
Italians used to sing all the time. Now, they only do it in Hollywood movies, Indian movies are mostly a series of songs and dances trapped around silly stories. As a result, they don’t do much singing in Indian villages anymore. Indeed, ever since radio first came to life, there has been a terrible decline in amateur (业余的) singing throughout the world.
There are two reasons for this sad decline. One, human beings are astonishingly lazy. Put a lift in a building, and people would rather take it than climb even two flights of steps. Similarly, invent a machine that sings, and people would rather let the machine sing than sing themselves. The other reason is that people are easily embarrassed. When there is a famous, talented musician readily available by pushing a button, which amateur violinist or pianist would want to try to entertain family or friends by himself
These earnest reflections came to me recently when two CDs arrived in the mail. They are historic recordings of famous writers reading their own works. It was thrilling to hear the voices from a long dead past in the late 19th century. But today, reading out loud anything is no longer common. Today, we sing songs to our children until they are about two, we read simple books to them till they are about five, and once they have learnt to read themselves, we become deaf. We’re alive only to the sound of the TV and the stereo (立体声音响).
I count myself extremely lucky to have been born before TV became so common: I was about six before TV appeared. To keep us entertained my mother had to do a good deal of singing and tell us endless tales. It was the same in many other homes. People spoke a language; they sang it, they recited it; it was something they could feel.
Professional actors’ performance is extraordinarily revealing. But I still prefer my own reading, because it’s mine. For the same reason, people find karaoke (卡拉OK) liberating. It is almost the only electronic thing that gives them back their own voice. Even if their voices are hopelessly out of tune, at least it is meaningful self-entertainment.