问题 选择题

老师在黑板上画出了如图所示的四个运动图象,问同学们这四个图象各表示什么运动?阿杜同学做了如下回答,其中错误的是(  )

A.

表示物体先沿负方向做匀减速运动,速度为零后又沿正方向做匀加速运动

B.

表示物体做匀速运动

C.

表示物体做匀减速运动

D.

表示物体做减速运动

答案

A、从图象可知,物体做匀速直线运动.故A错误.

B、位移随时间均匀增大,物体做匀速直线运动.故B正确.

C、从图象可知,物体先向正方向做匀减速直线运动,然后反向做匀加速直线运动.故C错误.

D、位移时间图线的切线斜率表示瞬时速度,从图线斜率可知,速度减小,知物体做减速运动.故D正确.

本题选错误的,故选AC.

阅读理解

When the traffic lights turn red, we will stop driving a car or crossing a street. Why is red used for traffic lights instead of other colors?

As we know, scattering(散射) happens when light goes through the air. For the same media(媒质), if the wavelength islong, the scattering will be short. If the wavelength is short, then the scattering will be long.

Of all lights we can see red has the longest wavelength, so the scattering is the weakest. That means the red light travels far. In fact, it travels farther on rainy days.

Using the red light can help drivers in farther areas sec the lights. It helps drivers stow down or stop in lime. If drivers don't see the red light until they are close, they may not be able to stop the car in time. An accident may happen Red can also excite people. We can act more quickly when we see the color red. In a word, red lights help drivers stop in time and help prevent accidents.

小题1: When the traffic lights turn ______, we will stop driving a car.

A. red    B green     C. yellow

小题2:According to the passage, the scattering of the red light is the _______.

A. longest    b. weakest       C. farthest

小题3: The underlined word "wavelength" means________ in Chinese.

A.波浪        B.光波      C.波长

小题4: What can the red light help drivers do?

A. It can help drivers in farther areas see the lights.

b. It can help drivers slow down or stop in time.

C.A and b

小题5:Which of the following is the best title?

A. Why do accidents happen

b. How does the red light travel

C. Why do we use red traffic lights

阅读理解

阅读理解。

     The summer vacation is over. It's true that time always flies fast during the vacation. The weather was

hot and I could not do much work, but I lived happily.

     As the afternoon was hot, I did my work in the morning. I used to get up at 6:30 and take a walk in

the garden for half an hour. After breakfast, I began reading English and Chinese and did some exercises

in maths, which took me three hours or more. I worked quite hard and made great progress (进步).

     I spent the afternoon outside. I went to swim and it was funny. I would not go home until it was about

five or six o'clock. Sometimes a friend of mine would come to see me and we would spend some hours

listening to music.

     In this way I spent my vacation happily. I not only studied well, but also became a good swimmer.

Now I am in good health and high spirits (精神).

1. What does the text mainly tell us?

A. How the writer spent his summer holiday.

B. What the weather was like in that summer.

C. When the writer got up in the morning.

D. Where the writer took a walk.

2. How long did it take the writer to do his homework?

A. Half an hour.              

B. Three hours or more.

C. Only one hour.            

D. Two hours and a half.

3. The writer spent most of the afternoon________.

A. listening to music        

B. visiting his friends

C. walking in the garden      

D. swimming

4. The writer had very good summer holidays because he ________.

A. worked very hard and made great progress

B. did his work well and became a good swimmer

C. got up early and went home late

D. liked swimming better than studying

5. Which of the following is NOT true?

A. The writer made progress in his lesson.

B. The writer took a walk for half an hour before breakfast.

C. The writer began studying as soon as he got up.

D. The writer spent more time swimming than listening to music.