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问题 计算题

如图所示，质量mB＝3．5kg的物体B通过一轻弹簧固连在地面上，弹簧的劲度系数k＝100N／m．一轻绳一端与物体B连接，绕过无摩擦的两个轻质小定滑轮O1、O2后，另一端与套在光滑直杆顶端的、质量mA＝1．6kg的小球A连接。已知直杆固定，杆长L为0．8m，且与水平面的夹角θ＝37°。初始时使小球A静止不动，与A端相连的绳子保持水平，此时绳子中的张力F为45N。已知AO1＝0．5m，重力加速度g取10m／s2，绳子不可伸长．现将小球A从静止释放，则：

（1）在释放小球A之前弹簧的形变量；

（2）若直线CO1与杆垂直，求物体A运动到C点的过程中绳子拉力对物体A所做的功；

（3）求小球A运动到底端D点时的速度。

答案

(1)0.1m

(2)7J

(3)2m/s

填空题

根据拼音写汉字。   

（1）它（老鼠）一看苗头不对，知道出来得不是时候，便（cāng）_______皇逃窜。  

（2）细菌的分裂能力可与旅鼠的繁殖能力相（pì）_______美。 

（3）北极旅鼠在天敌面前具有明显的挑（xìn）_______性。   

（4）我却怎么也笑不出，陷入了迷（wǎng）_______的沉思。   

（5）丹尼斯大约猜透了我的心思，收（liǎn）_______了笑容。 

（6）试图去寻找一块水草丰美的新领地而误入（qí）_______途。

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单项选择题

Anyone who doubts that children are born with a healthy amount of ambition need spend only a few minutes with a baby eagerly learning to walk or a headp toddler starting to talk. No matter how many times the little ones stumble in their initial efforts, most keep on trying, determined to master their amazing new skill. It is only several years later, around the start of middle or junior high school, many psychologists and teachers agree, that a good number of kids seem to lose their natural drive to succeed and end up joining the ranks of underachievers. For the parents of such kids, whose own ambition is often inseparately tied to their children’s success, it can be a bewildering, painful experience. So it is no wonder some parents find themselves hoping that ambition can be taught like any other subject at school.
It’s not quite that simple. "Kids can be given the opportunities, but they can’t be forced," says Jaequelynne Eccles, a psychology professor at the University of Michigan who led a study examining what motivated first-and-seventh-graders in three school districts. Even so, a growing number of educators and psychologists do believe it is possible to unearth ambition in students who don’t seem to have much. They say that by instilling confidence, encouraging some risk taking, being accepting of failure and expanding the areas in which children may be successful, both parents and teachers can reignite that innate desire to achieve.
Dubbed Brainology, the unorthodox approach uses basic neuroscience to teach kids how the brain works and how it can continue to develop throughout life. The message is that everything is within the kids’ control, that their intelligence is

malleable

.
Some experts say our education system, with its p emphasis on testing and rigid separation of students into different levels of ability, also bears blame for the disappearance of drive in some kids. Some educators say it’s important to expose kids to a world beyond homework and tests, through volunteer work, sports, hobbies and other extracurricular activities. "The crux of the issue is that many students experience education as irrelevant to their life goals and ambitions," says Michael Nakkula, a Harvard education professor who runs a Boston-area mentoring program called Project IF (Inventing the Future), which works to get low-income underachievers in touch with their aspirations. The key to getting kids to aim higher at school is to tell them the notion that classwork is irrelevant is not true, to show them how doing well at school can actually help them fulfill their dreams beyond it. Like any ambitious toddler, they need to understand that they have to learn to walk before they can run.

Some experts suggest that many kids lose ambition in school because they are ______

A．cut off from the outside world

B．exposed to school work only

C．kept away from class competition

D．labeled as inferior to others
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