平均速度定义式为,当极短时,可以表示物体在t时刻的瞬时速度,该定义应用了下列哪种

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问题:

平均速度定义式为,当极短时,可以表示物体在t时刻的瞬时速度,该定义应用了下列哪种物理方法  

A.等效替代法

B.微元法

C.控制变量法

D.极限思想法

考点:伽利略对自由落体运动的研究
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从国际的视角看,公众、企业、政府、国际资助机构、()是社会服务机构的传统资金来源。

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一棵二叉树第6层(根结点为第一层)的结点最多为______个。

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企业景气指数(2009年3季度)
企业景气指数 企业家信心指数
上季 本季 上季 本季
总体 115.9 124.4 110.2 120.1
工业 112.0 120.5 106.3 116.3
建筑业 128.9 134.5 126.2 133.8
交通运输、仓储和邮政业 108.5 116.9 106.6 115.1
批发和零售业 126.5 136.0 114.5 123.8
房地产业 119.6 126.3 116.7 126.4
社会服务业 109.0 124.1 99.6 118.5
信息传输、计算机服务和软件业 145.1 151.8 143.2 150.5
住宿和餐饮业 103.0 115.1 100.6 116.7

根据上述资料,以下表述正确的是( )。

A.2009年2季度,所有行业的企业景气指数均呈上升趋势

B.2009年3季度,住宿和餐饮业企业家信心指数比上季度增长16.1

C.2009年2季度,社会服务业的企业信心指数呈下降趋势

D.2009年3季度,在所给各个行业中,只有批发和零售业企业景气指数增加值低于企业家信心指数增加值

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If you are human, you can’t help but experience times when everything seems to be going wrong and you feel as if your life is completely out of control. It is during those “down times” that words of encouragement from family, friends, co-workers or even strangers can lighten your spirits. It is also during those times that destructive words can sink you deeper and deeper into depression.

For example, consider this story about a group of frogs who were traveling through the woods when two of them fell into a deep pit (坑). All of the other frogs gathered around the pit. When they saw how deep the pit was, they told the two unfortunate frogs they would never get out.

The two frogs ignored the comments and tried to jump out of the pit. The other frogs kept telling them to stop. Finally, one of the frogs took heed of what the other frogs were saying and simply gave up. He fell down and died. The other frog continued to jump as hard as he could. Once again the crowd of frogs shouted at him to stop the pain. The more they shouted, the harder he jumped and finally he made it to safety.

When he got out, the other frogs asked him why he continued to jump when they were all shouting at him to simply quit. The frog explained to them that he was a little bit deaf. He thought they were encouraging him the entire time.

Every time you have a chance to say either something positive or negative to another human being, do choose the chance to say something positive! Don’t let those opportunities get away from you. Your words have a large amount of power. Use them wisely. You really never know just how much they can mean to someone else.

68. The first paragraph tells us that words play an important part especially when         .

A. we stay with our family, friends and co-workers

B. we hear strangers say something to us

C. we get through hard times in life

D. we make some big mistakes

69. The underlined phrase “took heed of ” had the similar meaning with “     ”.

A. acted according to            B. had some doubt

C. held on to                   D. got used to

70. The more they shouted, the harder he jumped and finally he made it to safety. That’s because        .

A. he struggled to prove that they were wrong  

B. he thought they were encouraging him

C. he was angry with what they said              

D. he didn’t want to let them down

71. After reading the passage, readers should learn a lesson that        .

A. we can use encouraging words to help others out 

B. having a positive attitude is important in life

C. never give up until we win   D. we must believe in ourselves rather than others

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凡是不等厚度钢板的对接,均应将厚板做削薄处理()

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