问题 计算题

乌鸦喝水的故事大家都熟悉.假若它碰到的是一个放在水平地面上容积为800 cm3 的圆柱形容器(容器壁厚度不计),该容器的底面积为20 cm2 里面装有400 cm3 水,这只口渴的乌鸦将地上的小石块逐个投入瓶子内.当瓶内石块的总质量达到1kg时,水面刚好升到瓶口,乌鸦喝到了水.(g取10 N/kg)求:    

(1)瓶子内石块的总体积;    

(2)这时水对容器的压强;    

(3)瓶子内石块所受的浮力共为多大?

(4)这时容器对地面的压强共增加了多少?

答案

解(1)石块体积:V=V-V=4×10-4m3.      

(2)瓶子深度:h=      对容器底压强:P=ρgh=4×103Pa.    

(3)∵石块浸没;        

∴V=V;受到浮力:FgV=4N.    

(4)对地面增加压力ΔF(或F)=G=mg=10N.        

增加压强:Δp=ΔPa.

阅读理解

阅读理解。

     Anne and Joseph are talking about an interesting question. Why do some people change their names? There can

be many reasons. Hanna changed her name to Anne because she thought it would be easier for people to remember.

On the other hand, Joseph is thinking about changing his name to an unusual one because he wants to be different.

     People have a lot of   reasons for  changing their names.  Film stars, s ingers,  sportsmen and some other   famous

people often change their names because they want the names that are not ordinary, or that have special sound.

     Some people have another reason for changing their names. They have moved to a new country and want to use a

name that is usual there. For example, Li Kaiming changed his name to Ken Lee when he moved  to  the United States.

He uses the name Ken at school. But when staying with his family and Chinese friends, he uses Li Kaiming. For some

people, using different names makes life easier in their new country.

     In many countries, a woman changes her family names to her husband's  after she gets married.   But today, many

women are keeping their own family names and not using their husbands'.

1. Hanna changed her name to Anne because "Anne" _______.

A. makes her different

B. is easier for people to remember

C. is more unusual than "Hanna"

D. makes her prettier

2. Famous people want their new names to _______.    

A. have special sound

B. be ordinary

C. have no meaning

D. be unknown

3. Li Kaiming uses his new name when he _______.

A. stays with his family

B. is at school

C. is among Chinese friends

D. comes back to China

4. The underlined words "gets married" mean _______.   

A. 升官

B. 就业  

C. 结婚  

D. 生育

5. The passage mainly tells us _______.

A. different people have different names

B. what names mean

C. only film stars and sportsmen have two names

D. why some people change their names  

单项选择题