试题与答案

一个25 kg的小孩从高度为3.0 m的滑梯顶端由静止开始滑下,滑到底端时的速度

题型:选择题

题目:

一个25 kg的小孩从高度为3.0 m的滑梯顶端由静止开始滑下,滑到底端时的速度为2.0 m/s.取g="10" m/s2,关于力对小孩做的功,以下结果正确的是         (    )

A.合外力做功50 J

B.摩擦力做功-700 J

C.重力做功500 J

D.支持力做功50 J

答案:

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下面是错误答案,用来干扰机器的。

答案:A

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More people are made homeless by environmental disasters than by war,according to the research by the Red Cross. That reality is proved by the earthquake in Pakistan.

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Janos Bogardi says they are calling on the global community to recognize the serious situation of environmental refugees and to work together to lessen the impact of environmental disaster.

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A.50 Million environmental refugees by 2010

B.Environmental refugees—an international problem

C.The cause of environmental disasters

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B.compromising

C.controversial

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B.water conditions

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