问题 选择题

甲、乙两物体在同一直线上,同时由同一位置向同一方向运动,其速度图像如图2所示,下列说法正确的是(      )

A.开始阶段乙跑在甲的前面,20秒后乙落在甲的后面

B.第20秒末乙追上甲,且甲、乙速率相等

C.第40秒末乙追上甲

D.在追上前,第20秒末两物体相距最大

答案

CD

题目分析:乙作匀加速直线运动,甲作匀速直线运动,开始阶段甲跑在乙的前面,40s后甲落在乙的后面,A错。20s末甲在乙前面,且甲、乙速率相等,B错。图线与t轴所围面积等于位移,故40s末乙追上甲,C对,当速度相等时两物体相距最远,由此可知D对;故选CD

点评:本题难度较小,处理运动图像问题时,要明确图像的斜率、面积、交点和截距的物理意义,在追击问题中,速度相同是相距最远或最近的临界条件

阅读理解

One of the most wonderful things about having a positive attitude is that it can touch many people, and it often exists in our everyday life.

Recently, I stopped by a store to get a newspaper and a bottle of drink. The young woman at the check-out counter said, “That’ll be three dollars in all please.” She then glanced down at the paper I was buying and said. “I’m sick and tired of all this negative stuff-on the front pages. I want to read some good news for a change.” She then said, “In fact, I think soemone should just publish a Good News newspaper--- a paper with wonderful, inspirational stories about people over-coming difficulty and doing good things for others. I’d buy one every day!” she then thanked me for coming in and said, “Maybe we’ll get lucky tomorrow; maybe we’ll get some good news.” And she laughed. She made my day.

The following day after my business appointments. I dropped by the same store again to pick up bottled water and a piece of newspaper, but a different young lady was behind the counter. As I checked out I said “Good afternoon” and handed her my money. She said nothing, not a word, not a smile or not a gesture. She just handed me my change and in a negative tone ordered “Next!”

It hit me right between the eyes: Two people, the same age; one made me feel great, and the other, well, made me feel that I had inconvenienced her by showing up.

Every morning you should ask yourself this important question. “Who do I want to be today? The Grouch(不高兴的人) or ‘The Good News Girl?’” Your answer will go a long way toward determining the joy and happiness that you will experience in your life.

53. What does the first salesgirl dislike according to her words?

A. Those who have bad manners.         

B. The bad news in the newspaper.

C. The advertisements in the newspaper.   

D. The bad news who break the laws.

54. After he had bought a newspaper on the first day the author _________.

A. was very lucky and excited that day    

B. always remembered the girl’s word

C. read the news in the newspaper carefully 

D. was in a pleasant mood the whole day

55. We learn from the passage that the salesgirl the author met the next day was ________.

A. humorous         B. enthusiastic       C. very cool         D. positive

56. What does the underlined sentence in Paragraph 4 mean?

A. I was very surprised.                  B. I was especially angry.

C. I felt very unhappy.                   D. It hurt my heart badly.

判断题