问题 多选题

某人在静止的湖面上某高度处竖直上抛一个铁球,铁球上升到最高点后自由下落,穿过湖水并陷入湖底的淤泥中一段深度(假设泥中阻力大小恒定).不计空气阻力,以v、F、Ek分别表示小球的速度、所受合外力和动能三个物理量的大小.下列图象中能正确反映小球运动过程的是(  )

A.

B.

C.

D.

答案

A、小球在空中先做竖直上抛运动,再做自由落体运动,速度随时间先均匀减小,再反向均匀增加;进入湖水后加速度减小,但仍会做加速运动;进入淤泥后开始减速运动,故速度图象应为A,故A正确,B错误;

C、小球在空中运动过程中只受重力,方向竖直向下;而进入水中后,受力减小,合力方向向下,而进入淤泥后合力向上,故C正确;

D、小球的动能Ek=

1
2
mv2,在空中运动时为匀变速直线运动,v=gt,故动能和时间为二次函数关系,故D错误;

故选AC.

完形填空
完形填空
     My mother used to ask me what was the most important part of the body. Through the years I would
__1__what I thought was the correct answer. When I was younger, I thought __2__was very important to
us as humans, so I said, "My ears, Mommy". She said, "No. Many people are __3__. But you keep
thinking about it and I will ask you again soon."
     Several years passed __4__she asked me again. Since making my first __5__, I had often thought of
the correct answer. So this time I told her, "Mommy, sight is very important to everybody, so it must be
our eyes." She looked at me and told me, "You are __6__fast, but the answer is not correct because there
are many people who are blind."
    __7__the years, Mother asked me a couple more __8__and always her answer was, "No, but you are
getting __9__every year, my child." Then last year, my Grandpa died. Everybody was crying when it was
our __10__to say our final good-bye to Grandpa. Mom asked me, "Do you know the most important
body part yet, my dear?"
     I was __11__when she asked me this now. I always thought this was a __12__between her and me.
She saw the__13__on my face and told me, "This question is very important. It shows that you have really
__14__your life." I saw her eyes well up with tears. She said, "My dear, the most important body part is
your __15__." I asked, "Is it because it holds up your head?" She replied, "No, it is __16__on them a
crying friend or loved one can rest their head. I only hope that you have enough __17__and friends that
you will have a shoulder to cry __18__when you need it." Then and there I knew the most important body
part is not a __19__one. It is sympathetic to the pain of __20__.
( )1. A. notice    
( )2. A. love      
( )3. A. blind    
( )4. A. while    
( )5. A. discovery
( )6. A. learning  
( )7. A. Before    
( )8. A. ways      
( )9. A. stronger  
( )10. A. duty    
( )11. A. shocked  
( )12. A. game    
( )13. A. worry    
( )14. A. enjoyed  
( )15. A. shoulders
( )16. A. how      
( )17. A. respect  
( )18. A. by      
( )19. A. valuable
( )20. A. others  
B. believe    
B. health    
B. deaf      
B. once      
B. decision  
B. thinking  
B. Till      
B. things    
B. taller    
B. turn      
B. satisfied  
B. test      
B. puzzlement
B. found      
B. feet      
B. because    
B. favor      
B. on        
B. useful    
B. the deaf  
C. doubt    
C. sound    
C. lame      
C. after    
C. attempt  
C. growing  
C. Beyond    
C. questions
C. smarter  
C. pity      
C. interested
C. match    
C. regret    
C. disliked  
C. hands    
C. why      
C. love      
C. above    
C. selfish  
C. Grandpa  
D. wonder    
D. sight    
D. foolish  
D. before    
D. suggestion
D. changing  
D. Over      
D. times    
D. nicer    
D. chance    
D. excited  
D. job      
D. pain      
D. lived    
D. hair      
D. whether  
D. fun      
D. for      
D. precious  
D. the blind
单项选择题