问题 计算题

如图所示, 为固定在绝缘水平面上两平行光滑金属导轨,导轨左端间接有阻值为=导线;导轨右端接有与水平轨道相切、半径内壁光滑的半圆金属轨道。导轨间距,电阻不计。导轨所在平面区域内有竖直向上的匀强磁场。导轨上长度也为、质量、电阻=的金属棒=速度进入磁场区域,离开磁场区域后恰好能到达半圆轨道的最高点,运动中金属棒始终与导轨保持良好接触。已知重力加速度=。求:

(1)金属棒刚滑出磁场右边界时的速度的大小;

(2)金属棒滑过磁场区的过程中,导线中产生的热量

答案

(1)(2) 

题目分析:(1)在轨道的最高点,根据牛顿定律

              ①

金属棒刚滑出磁场到最高点,根据机械能守恒

     ②

由①②式代入数据解得

                    ③

(2)对金属棒滑过磁场的过程中,根据能量关系

       ④

对闭合回路,根据热量关系

            ⑤

由④⑤式并代入数据得

                  ⑥

点评:考查的问题较多,但多为基础知识的应用,掌握好法拉第电磁感应定律、安培力、圆周运动及电路的性质即可顺利求解.

完形填空

第二节 完形填空(共20小题;每小题1分,满分20分)

请认真阅读下面短文,从短文后各题所给的A、B、C、D四个选项中,选出最佳选项,并在答题卡上将该项涂黑。

Think you can’t be happy? You’ll think again after reading this story.

Barbara Ann Kipfer hated her feet. They were too big and she always seemed to   36   over them when someone was   37   —usually a smart guy. Come to think of it, her teeth were too big, too. The other kids teased her because of the way she   38   and because she wanted to be a sportswriter some day. No matter what she did, she was teased for being “  39  .”

That’s   40   she started writing down things that she liked in a notebook. “It was like a friend, and it   41   me that there are good things,   42   everything around me is unpleasant,” she says. She copied the list over and over,   43   new things every day.

One day, she decided to   44   her list with some of the girls in her class, hoping they would think it was as much fun as she did. But   45  , they made her feel stupid again. “They laughed at me,” she remembers, “I was ashamed, and I   46   doing it.” Here comes the  47  part. When she was in 10th grade, Kipfer found her old notebook and decided to   48   where she left off. “It was like a diary, like a photograph of my life,” she says. She started writing to publishers, asking them if they’d be interested in printing her list as a book.

She kept writing to one company   49  , because she liked the types of books it printed. “He kept saying, ‘It’s just a list, what am I supposed to do with it?’” “You’re not   50   to do anything with it. It’s   51   supposed to remind people of something they did that was really  52  .”

Finally, the publisher   53   to turn Kipfer’s list into a book, which sold more than million copies! 14,000 Things to Be Happy About even   54   it to be New York Times Best Sellers list.   55   being a best-selling author, Kipfer also went to realize her dream of becoming a sports editor at the Chicago Tribune.

36. A. jump                         B. fall                          C. turn                         D. push

37. A. nearby                       B. around                            C. watching                  D. laughing

38. A. dressed                      B. lived                        C. thought                    D. looked

39. A. foolish                      B. special                            C. different                   D. shy

40. A. what                         B. when                       C. because                    D. where

41. A. reminded                   B. told                         C. persuaded                 D. helped

42. A. because                            B. but                          C. unless                      D. even though

43. A. adding                       B. finding                     C. making                    D. giving

44. A. talk                           B. discuss                     C. share                        D. write

45. A. then                          B. naturally                  C. further                            D. instead

46. A. continued                  B. stopped                    C. enjoyed                    D. hated

47. A. cool                          B. important                 C. exciting                    D. funny

48. A. find out                            B. pick up                    C. think of                    D. give up

49. A. in general                  B. at first                      C. in particular              D. at last

50. A. made                         B. going                       C. advised                    D. supposed

51. A. often                         B. just                          C. also                         D. always

52. A. excellent                    B. successful                 C. fun                          D. true

53. A. hoped                        B. agreed                      C. refused                     D. considered

54. A. made                         B. expected                  C. hoped                      D. helped

55. A. Without                            B. Instead of                 C. While                      D. Besides

单项选择题