问题 选择题

如右图所示,滑轮A可沿倾角为的足够长光滑轨道下滑,滑轮下用轻绳挂着一个重力为G的物体B,下滑时,物体B相对于A静止,则下滑过程中              (   )

A.B的加速度为gsin

B.绳的拉力为Gsin

C.绳的方向保持竖直

D.绳的拉力为G

答案

答案:A

整体具有相同的加速度,对整体分析,a= gsin.隔离对B分析,B的加速度为gsin,方向与斜面方向平行且向下,根据平行四边形定则,绳子的拉力T=Gcos,绳子的方向与斜面垂直。故A正确,B、C、D错误。

故选A。

阅读理解

阅读理解 。

  Pubs are an important part of British life. E-ven very small villages always

have one. People,especially men, often go to a pub for a drink in thesame pub.

Women now go to the pubs more thanthey used to, butthey usually don't like to go

to apub on their own. Children under 16 are usuallynot allowed to go to the

pubs.      

  Until 1988, pubs were only open from 12 amto 2 pm. When it's nearly time

for the pub toclose, the owners shout "last orders" and the"time". Pubs also sell

food or snacks, Typical pubfood is pie, chicken and chips, and bread with

cheese.  Pubs have names.  Here is often a sign out-side the pub shoWing the

name with a picture.Many pubs have two or more different bars. Thepublic bar

often has a pool table and

dartboard(飞镖). Local people usually go to such kind of bar.The saloon bar is

comfortable and well-furnished.Men and women often go there drinking

together.                       

1. Who do you think will go to the pubs  more? 

A. Men.        

B. Women.        

C. Villagers.        

D. Children under 16.

2. Do women often go to the pubs alone?

A. Yes, they do.    

B. No, they don’t.  

C. Yes, they will.    

D. No, they didn’t.

3. How long were the pubs usually open before 1988 ?

A. For about 12 hours.    

B. For about 14 hours.    

C. For about 9 hours.

D. For about 2 hours.

4. Which of the following is TRUE? 

A. An eighteen-year-old boy can't go to the pubs.    

B. Women weren't allowed to go to the pubs on their own.    

C. Pubs sell food or snacks,but they don’t sell drinks.    

D. Local people usually like to go to the public bar.

5. What do you think. the public bar is like? 

A. It's more crowded and comfortable.   

B. It's comfortable and clean.    

C. It's more crowded than the saloon bar.

D. The drinks there are more expensive.

单项选择题