问题 填空题

如图所示,两木块A和B叠放在光滑水平面上,质量分别为m和M,A与B之间的最大静摩擦力为f,B与劲度系数为k的轻质弹簧连接构成弹簧振子.为使A和B在振动过程中不发生相对滑动,则它们的振幅不能大于______,它们的最大加速度不能大于______.

答案

当A和B在振动过程中恰好不发生相对滑动时,AB间静摩擦力达到最大.根据牛顿第二定律得:

   以A为研究对象:a=

f
m

以整体为研究对象:kA=(M+m)a

联立两式得,A=

(M+m)f
km

故答案为:

(M+m)f
km
f
m

完形填空

第二节完形填空  (共20小题,每小题1分,满分20分)

阅读下面短文,掌握其大意,然后从36至55各个题所给的四个选项A、B、C、D中,选出最佳选项,并在答题卡上将该项涂黑。

When we visit another country, differences in music and dance are   36   some of the first things that we notice. Every culture has   37   its own types of music and dance, which are very different from those of other societies.

Each type of music usually has a distinctive rhythm and a special sound,   38   on the kinds of instruments that are used to produce it. The most common type of instruments are   39   instruments, such as guitars and violins; wind instruments, including horns and flutes. Many different kinds of musical sounds   40   be created by using different combinations of instruments.

The human voice is a very special kind of instrument,   41   it can produce a great number of different sounds with different   42  , ranging from loud to soft. Singing is very popular in most cultures because it allows us to   43   words and ideas with music.

Societies coordinate body movements with musical rhythms to create   44  . Sometimes people dance for fun and individual expression. Dances can also be used to   45   ideas to an audience. Hawaiian dancers,   46  , use arm and hand movements to express the meaning of a song. In the same way, many societies use dances in religious ceremonies   47   to tell about important events.

Music and dance are passed from one   48  to another and thus become a permanent part of the society and   49   culture. Of course, as cultures come   50   contact with each other, the music and dance of one society may be accepted by other societies, or the different styles may be combined to   51   a new kind of music or dance. Some Latin American music, for example, has taken   52   from Indian cultures and mixed them with those from European and African cultures.   53  , popular music from England and the US can be heard in countries   54   the world,   55   it has had an influence on musical tastes, especially among young people.

36. A. unlikely       B. likely  C. probably    D. surely

37. A. installed       B. meant    C. developed       D. established

38. A. focusing      B. depending  C. playing        D. resting

39. A. thread   B. string  C. cord   D. band    

40. A. might   B. can    C. must   D. should   

41. A. when    B. after   C. since   D. although  

42. A. heights B. sizes   C. tones   D. volumes

43. A. explain B. express       C. provide      D. compose

44. A. sounds  B. songs  C. moves D. dances

45. A. give     B. communicate     C. translate     D. perform

46. A. such as B. for example       C. that is D. on the contrary

47. A. just      B. as       C. only    D. or

48. A. country B. generation  C. people D. time

49. A. their     B. its       C. form   D. the

50. A. to  B. for      C. into    D. with      

51. A. join      B. show   C. form   D. become

52. A. advantages   B. features      C. styles           D. origins

53. A. However      B. On the contrary  C.  Similarly D. Besides

54. A. over     B. through      C. across D. along

55. A. when    B. where C. which D. what     

多项选择题