题目

如图所示，灯重G=20N，AO与天花板间夹角α=30°，BO水平，试求AO，BO两绳受到的拉力各为多大？ 答案：40N    20 N 解析:=40N         ………（4分） =20 N  ………（4分）I looked closely at the face of my 23-year-old son, Daniel. In a few hours he would be 16 to France. He would be staying there for at least a year to learn another language and experience another style of 17 in a different country far from the USA. It was a(n)18 time in Daniel life, a step from college into the adult world. I wanted to 19 him some words that would have some meaning. But 20 came from my lips. I stood-frozen and quiet, looking into the searching eyes of my son. What 21 it more difficult was that I knew this was not the first time I had let such a moment 22. When Daniel was five, I took him to the bus stop on his first day of kindergarten. I felt the tension(紧张)in his hand 23 mine as the bus turned the corner. I saw his face turned red as the bus 24. He looked at me-as he did now. My father and I loved each other. Yet, I always regretted(后悔)never hearing him put his feelings into words and 25 having the memory of that moment. Why is it so hard to tell a 26 something from his heart? My mouth turned 27, and I knew I would be able to get out only a few words clearly. “Daniel,” I said, “If I could have picked, I would have picked you.” I wasn’t sure whether he understood 28 I meant. Then he came toward me and threw his 29 around me. For a moment, the world and all the people 30, and there was just Daniel and me in our home by the sea. （   ）16. A. flying                          B. shipping            C. riding              D. driving （   ）17. A. study                           B. life                    C. art                  D. fashion （   ）18. A. easy                            B. comfortable       C. boring        D. important （   ）19. A. record                     B. leave                   C. take                  D. write （   ）20. A. something                    B. everything  C. nothing          D. anything （   ）21. A. made                           B. caused              C. developed   D. improved （   ）22. A. remember                    B. pass                  C. forget        D. waste （   ）23. A. shaking                 B. catching         C. clapping         D. holding （   ）24. A. stopped                B. opened                 C. shook          D. drove （   ）25. A. always                  B. seldom                     C. usually              D. never （   ）26. A. father                      B. mother                C. daughter            D. son （   ）27. A. wet                      B. sour                         C. dry                   D. sweet （   ）28. A. what                       B. which                        C. where        D. that （   ）29. A. legs                      B. hands                C. arms              D. feet （   ）30. A. cheered                B. disappeared        C. laughed          D. cried