题目

 如图所示的结构装置可绕竖直轴转动，假若细绳长L=0.5m，水平杆长L0=0.2m，小球的质量m=0.4kg．求：（1）使绳子与竖直方向夹角角，该装置以多大角速度转动才行？（2）此时绳子的拉力为多大？（g=10m/s2，，）      答案： （1）（2）5N It was in my high school science class. I was doing a task in front of the classroom with my favorite shirt on.     A   41   came, “Nice shirt,” I smiled from ear to ear. Then another voice said, “That shirt belonged to my dad. Greg’s mother works for my family. We were going to   42   that shirt away, but gave it to her   43  .” I was speechless. I wanted to hide.     I   44   the shirt in the back of the closet and told my mum what had happened. She then dialed her   45  , “I will no longer work for your family,” she told him. That night, Mom told my dad that she couldn’t clean anymore; she knew her life’s   46   was something greater.     The next morning she   47   with the personnel manager at the Board of Education. He told her that without a proper education she could not teach. So Mom decided to   48   a university.     After the first year in college, she went back to the personnel manager. He said, “You are   49  , aren’t you? I think I have a   50   for you as a teacher’s assistant. This opportunity deals with children who are mentally challenged with little or no chance of   51  .” Mom accepted the opportunity very   52  .     For almost five years, as a teacher’s assistant, she saw teacher after teacher give up on the children and quit, feeling   53  . Then one day, the personnel manager and the principal   54   in her classroom. The principal said, “We have watched how you   55   the children and how they communicate with you and admire your hard-working   56   over the last five years. We are all in agreement that you   57   be the teacher of this class.”     My mom spent more than 20 years there.   58   her career, she was voted Teacher of the Year. All of this came about because of the   59   comment made in the classroom that day. Mom showed me how to handle   60   situations and never give up. 41. A. noise                         B. voice                       C. sound                              D. tune 42. A. get                            B. take                    C. carry                               D. throw 43. A. otherwise                   B. anyhow                    C. instead                            D. actually 44. A. settled                B. pushed                     C. stored                      D. stuck 45. A. teacher             B. employer                  C. director                     D. adviser 46. A. purpose                     B. encouragement     C. achievement                     D. victory 47. A. went                          B. met                  C. worked                           D. stayed 48. A. visit                          B. continue                   C. attend                      D. prepare 49. A. serious                B. fortunate                  C. careful                      D. responsible 50. A. career                        B. duty                         C. position                           D. part 51. A. learning                     B. judging                   C. obeying                      D. imagining 52. A. patiently                    B. eagerly                     C. successfully                     D. skillfully 53. A. upset                         B. frightened                C. guilty                              D. ashamed 54. A. looked up                  B went up                     C. took up                         D. showed up 55. A. believe               B. protect                 C. treat                       D. receive 56. A. spirit                         B. intention                  C. action                      D. attempt 57. A. must                        B. would                      C. might                            D. should 58. A. At                           B. During                     C. On                                D. With 59. A. worthless        B. thoughtless     C. hopeless                        D. helpless 60. A. challenging         B. different                   C. dangerous                      D. strange