问题 选择题

在研究下述运动时,能把物体看作质点的是(  )

A.研究地球的自转

B.研究自行车车轮的旋转

C.研究火车从南京到上海运行需要的时间

D.研究一列火车通过长江大桥所需的时间

答案

A、研究地球的自转时,地球有大小和形状不能忽略,不能看作质点,否则就无法分辨地球的转动.故A错误.

B、研究的是自行车车轮自身的旋转情况,转动的物体研究自身转动时,物体自身尺寸不能忽略,所以不可以看作质点,所以B错误.

C、研究火车从南京到上海的运动所需时间时,火车的长度能忽略,可以看成质点,所以C正确.

D、研究火车通过长江大桥所需时间时,火车的长度不能忽略,不能看成质点,所以D错误.

故选C.

选择题
完形填空

完形填空(共20小题,每小题1分,满分20分)

A while ago my family and I went sledding(滑雪橇) and as I watched my children climbing up the slope I started thinking.

Many people are convinced that most of today’s   26   problems are because of the “me” generation. Youngsters are just out for themselves and pay no   27   to others or their needs. Indeed, a common belief is that today’s youngsters won’t do anything  28   there is something in it for them.

Yet, while sledding, I saw a   29  side. I watched my two oldest children (then five and four) take my youngest(then two years old)by the hand to help her up the slippery slope  30   they went up. They would have been   31  without her, but not once did they try to sneak (溜掉)by her without helping. And when the sled  32  my two daughters was aimed toward the edge, it was my five year old son who ran to them to  33  them from falling and hurting themselves.

These children sometimes   34  among themselves and, on occasion, behave horribly. But I can  35  them shopping and know that they won’t ask for anything, I can talk to them about tsunami or hurricane victims and know that they will offer to  36  some of their own money to the cause, and I can ask them to play with those children  37  on the sideline(作为旁观者) and know that they will befriend(照顾)them.

Perhaps, therefore, the “me” generation is to blame  38   much of society’s problems—not the youngsters who want everything,   39  the adults who have taught them to selfishly  40   only of themselves.

Most adults have been   41  at some time or another, sadly, many   42  that disappointment down to their children. Then the children learn to put themselves first!

Most young children want to help. We can  43  that feeling by teaching the lesson my children learned while sledding: Life is a slippery slope with  44  of bumps(撞伤) and bruises(擦伤), but we can all make it to the  45  if we remember to help those who need it.

26.A.social         B.private                   C.serious                    D.slight

27.A.thought            B.attention                         C.permission             D.pleasure

28.A.if                                  B.as                             C.while                                 D.unless

29.A.same                          B.different                          C.strange                            D.moral

30.A.some time                 B.any time                          C.each time                        D.the time

31.A.faster                         B.slower                     C.easier                               D.lighter

32.A.containing                 B.loading                    C.driving              D.carrying

33.A.avoid                           B.stop                                  C.help                                   D.warn

34.A.cry                               B.cooperate                       C.assist                                D.fight

35.A.take                      B.drive                                 C.accompany            D.guide

36.A.lend                   B.send                                  C.collect                     D.pay

37.A.forgotten                   B.missed                    C.left                                    D.ignored

38.A.of                                 B.within                               C.on                             D.for

39.A.and                    B.but                                    C.thus                                  D.though

40.A.consider           B.speak                                C.believe                    D.think

41.A.depressed                 B.surprised                         C.disappointed                  D.embarrassed

42.A.extend                        B.intend                       C.pass                                  D.spread

43.A.encourage                 B.strengthen                      C.discourage                     D.approach

44.A.opportunities  B.occasions                  C.promises                         D.fates

45.A.top                     B.bottom                   C.middle                     D.tip