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问题 问答题

甲、乙两小孩各乘一辆小车在光滑水平面上匀速相向行驶，速率均为6 m/s，甲车上有质量m0="1" kg的小球若干个，甲和他的车及所带小球总质量为m1="50" kg，乙和他的车总质量为m2="30" kg.甲不断地将小球以16.5 m/s的对地水平速度抛向乙，并被乙接住，问甲至少要抛出多少个小球才能保证两车不相撞？（不考虑空气阻力）

答案

15个

设至少要抛出n个小球才能保证两车不相撞,以甲车和抛出的n个小球为系统,在整个抛出过程中动量守恒,则m1v=nm0v0+(m1-nm0)v甲                                   ①

式中v="6" m/s,v0="16.5" m/s,v甲为抛出n个小球后甲车的速度,以乙车和抛来的n个小球为系统,在整个接球过程中动量守恒,则nm0v0-m2v=(nm0+m2)v2                             ②

要使两车不相撞,则v甲≤v乙                                                    ③

代入数据解得:n=15.

材料分析题

小刚的爸爸与小明的爸爸合伙做生意，小刚的爸爸出资10万元，但不参与经营，小明的爸爸负责经营，但不出资。一年后赢利两万元。但是，在如何分配利润的问题上，两人发生了矛盾。多次协商并经他人调解，但仍无结果，最后两人通过法律途径使此事得到解决。

（1）什么是法律？

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（2）材料体现了法律的什么作用？法律还有什么其他作用？

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（3）法律面前，青少年应该怎样做？

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完形填空
A lady wanted a birthday gift from her husband. For many months she had liked a beautiful       , and knowing her husband could       it, she told him that was all she wanted. On the morning of the        , her husband told her how       he was to have such a good wife, and how much he loved her. He       her a beautiful gift package (纸盒). She opened it and       a Bible.      , she raised her voice and said to her husband, “With all your money, you give me a Bible?” She was so       that she left him.
Many years passed and the lady was very       in business. She owned two large companies. She     her husband was very old, and thought perhaps she should go to      him. But before she could, she      a letter telling her that he had died, and gave all of his possessions (财产) to her. She needed to come back and       things.
When she arrived at his house, sadness       her heart. She saw the still new       , just as she had left it years before. With       , she opened it and began to turn the pages. A ring       from the Bible to the floor and a       could be seen. She picked it up and found it was the ring she wanted in those days. And on the card was the date of her birth, and the words “LOVE U ALWAYS”.
      your gift is not packaged the way you want it, it’s because it is better packaged the way it is! Always appreciate little things; they usually lead you to bigger things! The best and most beautiful things in the world cannot be seen or even touched for they must be felt with the      .
小题1:
A．watchB．ringC．coatD．box
小题2:
A．affordB．likeC．designD．guess
小题3:
A．holidayB．performanceC．birthdayD．meeting
小题4:
A．proudB．kindC．sorryD．brave
小题5:
A．lentB．askedC．gaveD．moved
小题6:
A．carriedB．foundC．missedD．held
小题7:
A．PolitelyB．LightlyC．PatientlyD．Angrily
小题8:
A．calmB．upsetC．gratefulD．careless
小题9:
A．failingB．lonelyC．successfulD．poor
小题10:
A．wonderedB．hopedC．realizedD．explained
小题11:
A．visitB．understandC．catchD．help
小题12:
A．passedB．wroteC．sentD．received
小题13:
A．take care ofB．pay forC．look forD．give away
小题14:
A．coveredB．brokeC．leftD．filled
小题15:
A．carB．BibleC．letterD．table
小题16:
A．smilesB．laughterC．tearsD．interests
小题17:
A．hidB．droppedC．disappearedD．made
小题18:
A．bookB．penC．flowerD．card
小题19:
A．If B．ButC．AlthoughD．So
小题20:
A．handB．eyeC．faceD．heart
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