问题 选择题

向如图所示的玻璃瓶内注入水,然后将插有细玻璃管的软木塞塞紧玻璃瓶,玻璃瓶壁有A、B两个孔,也用软木塞子塞住.瓶内液面如图1所示,现将A、B处的木塞同时拔去后,则下列说法中正确的是(  )

A.A,B两孔中均无水射出

B.A,B两孔中均有水射出

C.A孔中无水射出,B孔中有水射出

D.A孔中有水射出,B孔中无水射出

答案

设玻璃管插入水的部分长度是L,设玻璃管下端为C点,又设大气压强是P0、瓶内上方气体压强是P1

又设A,B到水面距离分别是L1、L2

显然L2>L>L1,可以看到,玻璃管内没有水.也就是说,玻璃管内的水面在C点.因为C点上方是大气,所以在C点,有压强平衡关系:P0=P1+ρgL,

再看A点,塞子左边压强=P1+ρgL1<P1+ρgL=P0=塞子右边压强(即大气压),所以A点在拔掉塞子的瞬间没有水出来.

最后看B点,塞子左边压强=P1+ρgL2>P1+ρgL=P0=塞子右边压强(即大气压),所以B点在拔掉塞子的瞬间会出水.

故选C.

阅读理解

阅读理解。

     Once upon a time, there was an island where all the feelings lived: Happiness, Sadness, Knowledge, and

all of the others, including Love. One day the feelings were told that the island would sink, so all built boats

and left, except Love. Love was the only one who stayed. Love wanted to hold out (坚持) until the last

possible moment.

     When the island had almost sunk, Love decided to ask for help.

     Richness was passing by Love in a big boat. Love said, "Richness, can you take me with you?"

     Richness answered, "No, I can't. There is a lot of gold and silver in my boat. There is no place here for

you."

     Love decided to ask Vanity (虚荣心) who was also passing by in a beautiful ship. "Vanity, please help

me!"

     "I can't help you, Love. You are all wet and might damage (破坏) my boat," Vanity answered.

     Sadness was close by so Love asked, "Sadness, let me go with you."

     "Oh…Love, I am so sad that I need to be by myself!"

     Happiness passed by Love, too, but she was so happy that she did not even hear when Love called her.

     Suddenly, there was a voice,"Come, Love, I will take you." It was an elder. So thankful and happy, Love

even forgot to ask the elder where they were going. When they arrived at dry land, the elder went her own

way. Realizing how much was owed (欠) the elder, Love asked Knowledge, another elder, "Who helped me?"

     "It was Time, "Knowledge answered.

     "Time?" asked Love. "But why did Time help me?"

     Knowledge smiled with deep wisdom (智慧) and answered, "Because only Time is able to understand how

valuable (珍贵的) Love is."

1. How did the feelings go away from the island?

A. By water.

B. By swimming.

C. On foot.

D. By flying

2. How many feelings did Love ask for help but failed?

A. 2

B. 3

C. 4

D. 5

3. Which of the following is true?

A. Happiness was blind.

B. Richness had a small boat.

C. Vanity's ship was damaged.

D. Sadness wanted to stay alone.

4. Who saved Love?

A. Time.

B. Knowledge.

C. Richness.

D. Happiness.

5. Which of the following might be the best title of the passage?

A. Love and Time

B. An Accident

C. A sinking island

D. Different Feelings

单项选择题 B1型题