题目内容
Wind is the great maker of waves. There are exceptions, such as the tidal(潮汐的) waves some??times produced by earthquakes under the sea. But the waves most of us know are produced by winds blowing over the sea.
Now before constructing an imaginary life history of a typical wave, we need to know certain physical things about it. A wave has height, from trough (low point) to crest (high Point). It has length－the distance from this crest to that of the following wave. The period of the wave means the time it takes for succeeding crests to pass a fixed point. None of these things stays the same－for all depend upon the wind, upon the depth of the water and many other matters.
The water that makes up a wave does not advance with it across the sea. Each drop of water turns around in a little circle with the passing of the wave, but returns very nearly to its original position. And it is fortunate that this is so. For if the huge masses of water that make up a wave actually moved across the sea, sailing would be impossible.
If we want to find the speed of a wave, we may use the following way:
Speed = wavelength × frequency
Here, wavelength is the distance between two high points (crests), frequency means the number of cycles per second.
What causes waves?
A. Earthquakes and nothing else. B. Only wind.
C. Wind causes most waves. D. Wind causes some waves.
Which of the following is true according to the passage?
A. The water of a wave moves away across the sea.
B. The water of a wave remains almost at the same place.
C. The water of a wave goes with the passing of the wave.
D. The length of a wave means the distance from the top of a wave to the bottom.
The speed of Wave 1 is 100 cm/s, frequency 10. The frequency of Wave 2 is 300, while its speed is twice that of Wave 1. Which of the following is right?
A. The wavelengths of the two are equal.
B. The wavelength of Wave 1 is 10 times longer than that of Wave 2.
C. The wavelength of Wave 2 is longer than that of Wave 1.
D. The wavelength of Wave 1 is longer than that of Wave 2.
【小题1】C
【小题2】B
【小题3】D
解析:
略
天天向上一本好卷系列答案
小学生10分钟应用题系列答案| 完形填空。 | ||||
| I am not one who is frightened easily, but I must admit that one night I saw a figure th at really struck terror into my heart. I 1 it was a cold moon - lit night when I was walking home. It was the first night of my whole life that I had been outside 2 at such a late time. There were 3 few people on the road at night. Even during the day, the road was used by only some. On that night, it seemed even 4 . While I was walking, I could hear some 5 made by creatures that love the night world. I moved really fast towards home. It was 6 because I was hungry. More importantly, I was eager to get back home for warmth. All of a sudden, I 7 an old lady in a short distance away. Her 8 was covered with a white cloth. She was 9 to me, I think. I was a bit 10 . I wanted to know 11 she was there at that time of the late night. I stopped walking for a while. As I 12 there, stories about ghosts (鬼) began to come to my mind one after 13 . I was soon 14 fear and started to run as fast as I could. When I reached home I could 15 speak. The next day, however, I 16 that place again to make sure that the woman was not a ghost but indeed a real person. But I could find no footprints there 17 a banana plant. I realized then that it was the banana plant with its leaves moving in the gentle wind that 18 like a woman waving her hand. I had indeed made a fool of myself; but after the 19 night's experience, this 20 was small relief to me. | ||||
|