题目

利用物体自由落体运动，做《验证机械能守恒定律》的实验： （1）已备好的器材有：打点计时器，固定计时器用的夹子、铁架台、纸带，另外还有下列器材可供选择：低压直流电源、导线、复写纸片、天平、秒表等，其中不必要的器材是____________，还缺少的器材是________________ . (2)若应用公式v=gt计算即时速度进行验证，打点计时器所接交流电的频率为50赫兹，甲、乙两条实验纸带，如图所示，应选________纸带好.(3)若通过测量纸带上某两点间距离来计算 完形填空。      Here is a story about a clever dog.  It was a seeing-eye dog.  A seeing-eye dog can help blind (瞎的)  people walk along the streets and do many other things.      One day a seeing-eye dog and a blind man __1__ on bus together.  The bus was full of __2__ and  there were__3__ seats left.  But one man soon stood up and left his seat.  The dog __4__ the blind man  to the seat, but there was little space (空间) for two people.  The dog began to push the people on each  side __5__ his nose.  He pushed and pushed until the people moved and __6__ there was __7__ space  for two people.  The blind man than sat down and the dog got up on the seat at his side.  The dog  __8__ down and put his head on the leg of the __9__ man. He was very comfortable and soon fell  asleep.  Everyone on the bus __10__ at the dog. (     ) 1.  A.  got        (     ) 2.  A.  foreigners (     ) 3.  A.  no         (     ) 4.  A.  told       (     ) 5.  A.  for        (     ) 6.  A.  at first   (     ) 7.  A.  less       (     ) 8.  A.  went       (     ) 9.  A.  old        (     )10.  A.  smiled     B.  went       B.  policemen  B.  not many   B.  asked      B.  to         B.  still      B.  enough     B.  put        B.  blind      B.  watched     C.  came    C.  people  C.  enough  C.  carried C.  with    C.  at last C.  few     C.  lay     C.  young   C.  laughed D.  put     D.  farmers D.  some    D.  took    D.  at      D.  last    D.  litter  D.  jumped  D.  first   D.  looked