Science has told us so much about the moon that it is quite easy to form an idea of what it would be like to go there. It is certainly not a friendly place. As there is no air or water, there can be no life of any kind. Mile after mile there are only plains(平原) of dust with mountains around them. Above, the sun and stars shine in the black sky. If you step out of the mountains shadows, it will mean moving from terrible cold into great heat. The moon is also a very silent(安静的) world, for sound waves (声波)can only travel through air. But from the moon, you can see a friendly sight(景色). Our earth is shining more brightly than the stars. It looks like a large ball, coloured blue and green and brown.
( ) 16.What kind of place is the moon?
A. It is a friendly place. B. It is a lively place.
C. It is a nice place for man to live. D. It is a lifeless place.
( ) 17.Temperatures on the moon____.
A. are usually the same everywhere B. Are always very low
C. can be very different D. are usually very high
( ) 18.The moon is a silent world because____.
A. there is no life there B. there is no air there
C. there is no water there D. there is not a green tree there
( ) 19. When we look from the moon, the sky is ____.
blue B. black C. green D. brown
( ) 20. Mile after mile there are only plains of dust with mountains around them. The word “dust” means “___”.
A. dump (垃圾堆) B. dry earth (泥土) C. land D. field
。力F作用2s后撤去，物体在斜面上继续上滑了1.25s后速度减为零。求：物体在这段时间内的总位移s。(已知
＝0.6，
＝0.8，g＝10m/s2) 