问题 多选题

质点甲、乙均做直线运动,甲的x-t图象和乙的v-t图象如图所示,下列说法正确的是(  )

A.甲质点在3s内通过的位移为2m

B.甲质点在0-1s内做匀速直线运动

C.乙质点的加速度不变

D.乙质点沿直线向一个方向运动

答案

A、甲质点在3s内通过的位移为△x=2m-0=2m.故A正确.

B、由位移-时间图象的斜率等于质点的速度得知,0-1s内,甲质点的速度为零,表示质点处于静止状态.故B错误.

C、由速度-时间图象的斜率等于质点的加速度可知,乙质点的加速度大小为a=

△v
△t
=
10-0
1-0
m/s2=10m/s2
,保持不变.质点在奇数秒内的加速度为正值,表示加速度沿方向,而偶数秒内加速度为负值,表示加速度沿负方向,由于加速度是矢量,故质点的加速度是变化的.故C错误.

D、由图看出,速度的方向一直为正值,说明质点的运动方向一直沿正方向,即乙质点沿直线向一个方向运动.故D正确.

故选AD

阅读理解

阅读理解

    Several years ago, a television reporter was talking to three of the most important people in America.

One was a very rich banker, another owned one of the largest companies in the world, and the third

owned many buildings in the center of New York.

    The reporter was talking to them about being important.

    "How do we know if someone is really important?" the reporter asked the banker.

    The banker thought for a few moments and then said, "I think anybody who is invited to the White

House to meet the President of the United States is really important."

    The reporter then turned to the owner of the very large company. "Do you agree with that?" she

asked.

    The man shook his head, "No, I think the President invites a lot of people to the White House. You'd

only be important if while you were visiting the President, there was a telephone call from the president

of another country, and the President of the US said he was too busy to answer it."

    The reporter turned to the third man. "Do you think so?"

    "No, I don't," he said. "I don't think that makes the visitor important. That makes the President

important."

    "Then what would make the visitor important?" the reporter and the other two men asked.

    "Oh, I think if the visitor to the White House was talking to the President and the phone rang, and the

President picked up the receiver, listened and then said, 'It's for you.' "

1. This story happened in______.

A. England        

B. America        

C. Japan        

D. Australia

2. There are______ in this passage.

A. two men and two women              

B. three men and one woman

C. three women and one man              

D. four women

3. The banker thought______.

A. he was really important because he was a rich banker

B. the visitor to the White House to meet the President of the U.S was really important

C. the visitor who met the President of the US

D. the reporter was really important

4. The owner of the very large company thought______.

A. she was really important because she owned one of the largest companies

B. the banker was really important

C. the owner of many buildings in the center of New York was really important

D. the visitor would be really important if while he was visiting the President.the President would not

answer any telephone call

5. The owner of many buildings thought______.

A. he was really important because he owned many buildings in the center of New York

B. the owner of the very large company was really important

C. the visitor was really important if he was talking to the President and the President received a

telephone call for the visitor

D. the person who worked in the White House was really important

单项选择题