问题 选择题

质量为1kg的物体,以初动能120J从斜面的底端沿斜面向上运动,加速度大小为12m/s2,方向沿斜面向下,斜面倾角为30°,则物体在斜面运动的过程中,动能损失了(  )

A.20J

B.70J

C.100J

D.120J

答案

小物体上滑时的加速度a=

mgsin30°+μmgcos30°
m
=12m/s2.gsin30°=5m/s2,μgcos30°=7m/s2.mgsin30°<mgcos30°,物体上滑到最高点不再下滑,所以动能损失120J.故D正确,A、B、C错误.

故选D.

翻译题

完成句子

阅读下列各小题,根据所给的整句汉语提示,用句末括号的英语单词完成句子,并将答案写在相应题号后。

1. Seldom________each other any more though we studied and lived in the same town.(see)

     即使我们生活,学习在同一城市,我们也很少碰面

2. Could you possible let us know________?(as)

     你一决定,请尽快告诉我们好吗?

3. ________,and you can see Mt.baker hard against the Canadian border.(look)

    朝另一方向看,你可以看到紧靠着加拿大边界的贝克山.

4. In space the astronauts will have to face the circumstances ________on the earth.(train)

    在太空,航天员将不得不面对他们在地球上训练时的情形.

5. I don't want to get to the end of my life and find that ____________ just the length of it. I want to have lived the width of it as well.(live)

    我不想在生命终结的时候才发现我只活了生命的长度,我也想要活出生命的宽度.

6. "If China saw social and economic confusion,then________a disaster for the world."said Wen Jiabao.(be)

   " 如果中国经济和社会出现问题,将会给世界带来灾难. "温 * * 说.

7. By May 2008, the World bank was estimating that 100 million people subsistence poverty due to food inflation  in the first quarter of that year.(push)

    世界银行估计到2008年第一季度由于粮食价格的飞涨,有1亿人口陷入勉强维持生存的贫困状态.

8. I tell you in winter when there's no baseball, I stare out of the window,________.(wait)

    告诉你吧,在没有棒球的冬天,我就盯着窗外,等待春天的到来.

9. Kelly was born in China and grew up there.________she knows so much about China!(wonder)

    凯莉在中国出生长大.难怪她对中国知道得这么多!

10. ________in face of danger matters much in case of emergency. (stay)

     在紧急情况下,面对危险我们应该保持镇静,这一点至关重要.

单项选择题