问题 问答题

利用如图所示的方法测定细线的抗拉强度.在长为L的细线下端悬挂一只质量不计的小盒,小盒的左侧开一孔,一个金属小球从斜轨道上释放后,水平进入小盒内,与小盒一起向右摆动.现逐渐提高金属小球在轨道上释放的高度,直至摆动时细线恰好被拉断,并测得此时金属小球平抛运动的竖直位移h和水平位移S,若小球质量为m,试求该细线的抗拉断张力多大?

答案

小球做平抛运动,有:

h=

1
2
gt2

S=v0t

在金属盒中,重力和拉力的合力提供向心力,根据牛顿第二定律,有:

T-mg=m

v20
L

联立解得:

T=mg(1+

S2
2hL

答:该细线的抗拉断张力为mg(1+

S2
2hL
).

完形填空

第二节: 完形填空 (共20小题;每小题1分, 满分20分)

请认真阅读下面短文, 从短文后各题所给的A、B、C、D四个选项中, 选出最佳选项, 并在答题纸上将该项涂黑。

My friend Michelle is blind, but you’d never know it. She makes such good use of her other  36  , including her “sixth sense”, that she seldom gives the impression (印象) that she’s   37   anything. It’s really amazing.

Michelle   38   her children pretty much like the rest of us, except that she isn’t too hard on them.   Her children really benefit a lot from her   39   attitude. She knows when to clean the house, and she moves around so fast that   40   often don’t realize she’s blind.

I   41  this the first time after my six-year-old daughter, Kayla, went to play there. When Kayla came home, she was very   42   about her day. She told me they had baked cookies, played games and done art projects. But she was   43   excited about her finger-painting project.

“Mom, guess what?” said Kayla, all smiles. “I learned how to   44    colors today! Blue and red make purple, and yellow and blue make green! And Michelle   45   with us”. 

To my great   46  , my child had learnt about color from a blind friend! Then Kayla continued, “Michelle told me my   47  showed joy, pride and a sense of accomplishment (成就). She really  48   what I was doing!” Kayla said she had never known how good finger paints felt   49   Michelle showed her how to paint without looking at her paper.

I realized Kayla didn’t know that Michelle was blind. It had just never come   50   in conversation. When I told my daughter Michelle was blind, she was   51   for a moment. At first, she didn’t believe me. “But Mommy, Michelle knew exactly what was in my picture!” Kayla   52  . I knew my child was   53   because Michelle had listened to Kayla describe her art work. Michelle had also “heard” Kayla’s   54  in her work.

We were silent for a minute. Then Kayla said slowly, “You know, Mommy, Michelle did ‘see’ my picture. She just used my   55  .” Indeed, she uses a special type of “vision” that all mothers have.

36. A. ways                         B. means                      C. methods                   D. senses

37. A. enjoyed                            B. found                       C. missed                     D. held

38. A. comes across                     B. looks after                C. picks out                  D. learns from

39. A. relaxed                      B. nervous                    C. anxious                    D. secret

40. A. parents                      B. family                      C. guests                      D. friends

41. A. realized                     B. heard                       C. forgot                      D. witnessed

42. A. sad                           B. calm                        C. excited                     D. puzzled

43. A. especially                   B. seldom                     C. frequently                D. hardly

44. A. paint                         B. draw                        C. create                       D. mix

45. A. stayed                        B. painted                    C. talked                      D. competed

46. A. excitement                 B. encouragement          C. delight                            D. surprise

47. A. attitude                      B. color                        C. picture                    D. paper

48. A. touched                            B. considered                C. saw                         D. understood

49. A. after                          B. unless                      C. until                        D. if

50. A. up                             B. down                             C. back                        D. on

51. A. curious                      B. quiet                       C. angry                       D. worried

52. A. whispered                  B. insisted                    C. introduced                D. informed

53. A. right                         B. wrong                      C. worried                    D. uncertain

54. A. shortcomings              B. difficulties                C. pride                       D. disappointment

55. A. paper                         B. pens                         C. hands                       D. eyes

单项选择题 A1/A2型题