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小车在水平面上向左作直线运动,车厢内用OAOB两细线系住小球。球的质量m=4千克。线OA与竖直方向成q=37°角,线OB水平。如图所示。g取10米/秒2,求:

【小题1】小车以5米/秒的速度作匀速直线运动,求OAOB两绳的张力?
【小题2】当小车改作匀减速直线运动,并在12.5米距离内速度降为零的过程中,OAOB两绳张力各多大?
【小题3】使OB绳所受拉力为零时,小车的加速度大小。

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翻译下列词汇。
1. 人,家伙 
2. 商店,店铺
3. 埃及
4. 油漆
5. 细绳
_____
_____
_____
_____
_____
6. 计划
7. 测试,实验  
8. 捆绑 
9. 连接
10. 装饰
_____
_____
_____
_____
_____

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如右图所示,一人坐在小车的水平台面上,用水平力拉绕过定滑轮的细绳,使人和车以相同的加速度向右运动,水平地面光滑(   )
A.若人的质量大于车的质量,则车对人的摩擦力方向向右
B.若人的质量小于车的质量,则车对人的摩擦力方向向右
C.若人的质量等于车的质量,则车对人的摩擦力为零
D.不管人、车的质量关系如何,车对人的摩擦力都为零

如右图所示,一人坐在小车的水平台面上,用水平力拉绕过定滑轮的细绳,使人和车以相同的加速度向右运动,水平地面光滑(   )
A.若人的质量大于车的质量,则车对人的摩擦力方向向右
B.若人的质量小于车的质量,则车对人的摩擦力方向向右
C.若人的质量等于车的质量,则车对人的摩擦力为零
D.不管人、车的质量关系如何,车对人的摩擦力都为零

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A young father was visiting an old neighbor. They were standing in the old man’s garden, and talking about children. The young man said,“How strict should parents be with their children?”
  The old man pointed to(指着)a string (细绳) between a big strong tree and a thin young one.
 “Please untie (解开) that string.” said the old man. “But first pull the string tight so that(以便于)the young tree is straight again.” The young man did so. He untied the string and only found that the young tree bent(弯)over to one side.
 Then the old man said,“There, it is the same with children. You must be strict with them. But sometimes you must untie the string to see how they are getting on. If they are not yet able to stand alone,you must tie the string tight again. But when you find that they are ready to stand alone,you can take the string away.”

  1. 1.

    The story is about _______.
        

    1. A.
      how to take care of young trees    
    2. B.
      how strict parents should be with their children
    3. C.
      how the young father should get on with his old neighbor
  2. 2.

    The young man untied the string _______.
        

    1. A.
      in order to throw it away  
    2. B.
      so that both of the trees wouldn’t grow straight
          
    3. C.
      and found that the young tree bent over to one side
  3. 3.

    When could the string be taken away?
        

    1. A.
      When the old man left.   
    2. B.
      When the young man untied it next time.
         
    3. C.
      When the young tree grew strong enough.
  4. 4.

    At last the old man told the young man _________.
        

    1. A.
      that he should be strict with his children if they could not stand alone
          
    2. B.
      that he should always be strict with his children
          
    3. C.
      that he should be hard on his children
  5. 5.

    We learn that the big strong tree and the thin young one are like _________.

    1. A.
      the young father and the old neighbor   
    2. B.
      parents and their children
           
    3. C.
      the old neighbor and the children of young father

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A young father was visiting an old neighbor. They were standing in the old man’s garden, and talking about children. The young man said,“How strict should parents be with their children?”
   The old man pointed to(指着)a string (细绳) between a big strong tree and a thin young one.
  “Please untie (解开) that string.” said the old man. “But first pull the string tight so that(以便于)the young tree is straight again.” The young man did so. He untied the string and only found that the young tree bent(弯)over to one side.
  Then the old man said,“There, it is the same with children. You must be strict with them. But sometimes you must untie the string to see how they are getting on. If they are not yet able to stand alone,you must tie the string tight again. But when you find that they are ready to stand alone,you can take the string away.”
【小题1】The story is about ____________.
      A. how to take care of young trees    
B. how strict parents should be with their children
C. how the young father should get on with his old neighbor
【小题2】 The young man untied the string ________________.
      A. in order to throw it away    
B. so that both of the trees wouldn’t grow straight
      C. and found that the young tree bent over to one side
【小题3】When could the string be taken away?
      A. When the old man left.     
B. When the young man untied it next time.
     C. When the young tree grew strong enough.
【小题4】 At last the old man told the young man ________________.
      A. that he should be strict with his children if they could not 
stand alone
      B. that he should always be strict with his children
     C. that he should be hard on his children
【小题5】We learn that the big strong tree and the thin young one are like _________.
A. the young father and the old neighbor     
B. parents and their children
       C. the old neighbor and the children of young father

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