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问题 单项选择题

低合金钢气焊时，采取焊前预热，选择较大型号的焊炬、喷嘴，（）都可有效地防止淬硬组织的产生。

A、适当降低焊接速度

B、加快焊接速度

C、减小火焰能率

D、在低温环境下焊接

答案

参考答案：A

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IV. 任务型读写
请认真阅读下面短文，并根据所读内容在文章后表格中的空格里填上最恰当的单词。注意：每空格1个单词。
The ups and downs of life may seem to have no predictable plan. But scientists know there are very definite patterns that almost all people share. Even if you’ve passed some of your “prime”, you still have other prime years to experience in the future. Certain important primes seem to peak later in life. It is really good news to many of us who don’t have a good feeling about ourselves now. We needn’t be worried about it now. When are you smartest? From 18-25, according to IQ scores; but you’re wiser and more experienced with increasing age.
You’re sharpest in your 20’s; around 30, memory begins to decline. But your IQ for other tasks climbs. Your vocabulary at the age of 45, for example, is three times as great as when you graduated from college. At the age of 60, your brain possesses almost four times as much information as it did at the age of 21. It is really amazing, but it is true.
When are you happiest? You have the best physical sense of yourself from 15 to 24; the best professional sense from 40 to 49.
Before age 24, we believe that our happiest years are yet to come; over 30, we believe that they’re behind us.
When are you most creative? Generally between 30 and 39, but the peak varies with different professions.
Mozart wrote a symphony and four sonatas by age eight, and Mendelssohn composed his best known work A Midsummer Night’s Dream, at 17, but most of the great music was written by men between 33 and 39.
Though the peak in most fields comes early-most Nobel prizewinners did their top research in their late 20’s and 30’s — creative people continue to produce quality work throughout their lives. For the “well-conditional mind”, there is no upper limit.
So if you are not very successful at present, it really doesn’t matter. Just have a little patience and wait for your best time.
Title: Best time in life
The smartest age
We have the (56)       IQ between the (57)        of 18 and 25.
The sharpest age
We are sharpest in our 20’s.
We have the (58)          vocabulary at the age of 45.
We possess the largest (59)          of information at the age of 60.
The happiest age
We are happiest at a time (60)         the age of twenty and         (61)          the age of 30.
The most creative age
Most of us have the greatest (62)         ability between the ages of 30 and 39.
Most people (63)         their Nobel Prizes in their late 20’s and 30’s.
People with well-conditioned (64) ________ are creative             (65)          their lives.
 
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实验题

利用如图所示的装置可以探究系统机械能守恒，在滑块B上安装宽度为L（较小）的遮光板（遮光板质量忽略不计），把滑块B放在水平放置的气垫导轨上，通过跨过定滑轮的绳与钩码A相连，连接好光电门与数字毫秒计，两光电门间距离用S表示。数字毫秒计能够记录滑块先后通过两个光电门的时间、，当地的重力加速度为g。请分析回答下列问题：

（1）为完成验证机械能守恒的实验，除了上面提到的相关物理量之外，还需要测量的量有_____________（均用字母符号表示，并写清每个符号表示的物理意义）；

（2）滑块先后通过两个光电门时的瞬时速度=_____________、=_____________（用题中已给或所测的物理量符号来表示）；

（3）在本实验中，验证机械能守恒的表达式为：_____________（用题中已给或所测的物理量符号来表示）。
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