题干

如图所示,一质量m2=0.25的平顶小车,车顶右端放一质量m3=0.2kg的小物体,小物体可视为质点,与车顶之间的动摩擦因数μ=0.4,小车静止在光滑的水平轨道上.现有一质量m1=0.05kg的子弹以水平速度v0=12 3 m/s射中小车左端,并留在车中.子弹与车相互作用时间很短.若使小物体不从车顶上滑落,求:
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Questionnaire
Read the questions and answer Yes or No , then you will find out how good you are.
1.  When you don’t understand something, you ask questions.
2.  You like listening to older people talk about the past.
3.  You think that you can learn something interesting from everyone around you.
4.  You are brave enough when you have to talk to people you don’t know.
5.  You enjoy reading books about famous people.
6.  You always see and talk to different people.
7.  You are interested in learning new ways of doing things.
8.  You enjoy sharing experiences with friends and learning from people of all ages.
9.  You talk a lot about yourself.
10. Even if you are often wrong, you make your own decisions.
11. You hate teaching what you are good at: sports, technology, whatever.
12. Your parents don’t understand you, so you don’t talk to them much.
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Score 2 points if you answer YES to each of the first 8 questions, and 0 if you choose NO.
Score 2 points if you answer NO to each of the last 4 questions, and 0 if you choose Yes.
18-24 You are friendly and open-minded. You make people feel important by listening to what they have to say. You’ll probably succeed in learning all kinds of interesting things. Good for you!
10-16 Remember that every single person you know can teach you something. You will greatly make your life rich and colorful.
0-8 About 400 years ago, a famous writer wrote , “No man is an island.” This is still true today. Try to be more open and interested in people around you.