问题 选择题

一个质点沿直线运动,第一秒内的位移是1m,第2秒内的位移是2m,第3秒内的位移是3m,第4秒内的位移是4m,则(  )

A.质点第1秒末速度是1m/s

B.质点前2秒内的平均速度是2m/s

C.质点第3秒内的平均速度是3m/s

D.质点4秒内的平均速度是4m/s

答案

A、因为不知道质点的运动状况,所以无法判断1s末的速度.故A错误.

    B、质点在前2s内的位移为3m,所以平均速度

.
v
=
x
t
=
3
2
m/s=1.5m/s.故B错误.

    C、质点在第3秒内的位移是3m,所以平均速度

.
v
=
x
t
=
3
1
m/s=3m/s.故C正确.

    D、质点在4s内的位移为10m,所以平均速度

.
v
=
x
t
=2.5m/s.故D错误.

故选C.

阅读理解

阅读短文,选择正确答案。

     A man was looking for things of the old times. One day he came to a village and found a blue bowl. It looked

very old. The bowl was on the ground and a cat was drinking milk from it. A farmer, the owner of the cat, was

sitting beside the bowl. The man did not want the farmer to know that he was interested in the bowl. So he said

to him in a soft voice, "What a nice cat you have! Will you sell it to me?"

    "How much will you give me for the cat?" the farmer asked.

    "Thirty dollars. Would that be enough?" Later, the farmer agreed. After he paid the farmer, the man said,

"This cat is used to eating with his bowl. May I take this bowl with the cat?" But the farmer said,"I'm sorry I

can't give you the bowl. Thanks to the bowl, I have sold thirty cats."

1. What does the sentence "A man was looking for things of the old times" mean? [ ]

A. He lost things in the past and wanted to get them back.

B. He liked talking to old people.

C. He liked keeping old things.

2. Why did the man want to buy the cat? [ ]

A. He liked it better than the bowl.

B. It was sold with the bowl.

C. He thought he could easily get the bowl after he bought the cat.

3. After he bought the cat, the man asked for the bowl, because he thought            .[ ]

A. the cat couldn't live without the bowl

B. the farmer didn't know the value of the bowl

C. the bowl should go with the cat

4. The farmer kept the bowl so that he could             . [ ]

A. let another cat use it

B. sell more cats

C. sell more bowls

5. From the story we can see that the farmer            . [ ]

A. had only one bowl

B. didn't like cats

C. was cleverer

问答题