问题 选择题

如图所示,斜面体A位于光滑水平面上,物块B在其斜面上静止。现给A施加一随时间t增大的水平力F,使A和B一起向左做变加速直线运动。则在B与A发生相对运动之前的一段时间内

 

A.B对A的压力和摩擦力均逐渐增大

B.B对A的压力和摩擦力均逐渐减小

C.B对A的压力逐渐增大,B对A的摩擦力逐渐减小

D.B对A的压力逐渐减小,B对A的摩擦力逐渐增大

答案

答案:D

题目分析:由于A、B一起向左做加速度a越来越大的加速运动,对B进行受力分析如图所示

将力在水平方向的竖直方向正交分解,则,由于a越来越大,因此摩擦力f与支持力FN差值越来越大,而又由于可知,竖直方向合力保持不变,因此一定是摩擦力f越来越大,而支持力FN越来越小,因此D正确,ABC错误。

完形填空

第二节   完形填空(共20小题,每小题1.5分,满分30分)

Be careful of those who use the truth to deceive (cheat). When someone tells you something that is true, but  36  important information that should be included, he can create a false  37  .

For Example, a man once told me, “I just won a hundred dollars on the  38  . It was great. I   39  that ticket back to the store and turned it in   40  one hundred dollars!”

This guy is a winner, right? May be, may be not. Then  41  I discovered that he bought two hundred tickets, and only one was a  42  . He was  43  a big loser!

He didn’t say anything that was false,  44  he left out important information  45  . That’s called a half—truth. Half—truths are not technically  46  , but they are just as dishonest.

Untrustworthy candidates in political campaigns often use this  47  . Let’s say that during Governor Smith’s last term, her  48  lost one million jobs and gained three million jobs. Then she sought another  49  . One of her opponents put an ad saying, “During Governor Smith’s term, the state lost one million jobs!” That’s  50  . However, an honest statement would have been quite different.

Advertisers will sometimes use half—truths. It’s  51  the law to make false claims, so they  52  to mislead you with the truth. An ad  53  blow its own horn, “Nine out of ten doctors lend Yucky Pills to cure nose pimples.” It fails to mention that they only ask ten  54  , and nine of them work for the Yucky Corporation.

This kind of  55  deception happens too often. It’s a fact of life: lies are lies, but sometimes the truth can lie as well.

36. A. makes out           B. leaves out                 C. tries out            D. puts out

37. A. chance            B. expression            C. impression     D. translation

38. A. spot                    B. lab                           C. competition          D. lottery

39. A. took                   B. turned                  C. went                 D. looked

40. A. with                   B. as                               C. like                   D. for

41. A. later                   B. formerly                  C. hardly           D. generally

42. A. loser                   B. winner                        C. shame           D. surprise

43. A. wrongly                 B. usually                  C. really                D. right

44. A. since                  B. what’s more                 C. therefore           D. but

45. A. on purpose      B. by accident        C. in time                 D. at first sight

46. A. chats                  B. lies                          C. failures             D. consequences

47. A. fair                       B. court                        C. trick             D. entry

48. A. company             B. fellow                  C. country             D. state

49. A. term                   B. cooperation                 C. election             D. service

50. A. boring                B. shocking                  C. true                  D. wrong

51. A. for                        B. against                        C. through             D. across

52. A. regret         B. forget              C. fail                   D. try

53. A. must                   B. need                        C. should           D. might

54. A. customers           B. patients                    C. reporters           D. doctors

55. A. attractive            B. critical                        C. fair                   D. Sad

单项选择题