题干

卡车原来以10m/s的速度在平直公路上匀速行驶,因为路口出现红灯,司机从较远的地方立即开始刹车,使卡车匀减速前进.当车减速到2m/s时,交通灯恰好转为绿灯,司机当即放开刹车,并且只用了减速过程一半的时间卡车就加速到原来的速度.从刹车开始到恢复原速的过程用了12s,求:

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同类题1

   As a child, I was really afraid of the dark and of getting lost. These fears were very real and caused me some uncomfortable moments.
   Maybe it was the strange way things looked and sounded in my own room at night that scared me so much. There was never complete darkness, but always a streetlight or passing car lights, which made clothes on the back of a chair take on the shape of a wild animal. Out of the corner of my eye, I saw the curtains seem to move when there was no wind. A very low sound in the floor would seem a hundred times louder than in the day. My imagination (想象) would run wild, and my heart would beat fast. I would lie very still so that the “enemy” would not discover me.
   Another of my childhood fears was that I would get lost, especially on the way home from school. Every morning I got on the school bus right near my home. That was no problem. After school, though, when all the buses were lined up along the street, I was afraid that I would get in the wrong one and be taken to some other strange places. On school or family trips to a park or a museum, I wouldn’t let the leaders out of my sight.
   Perhaps one of the worst fears of all I had as a child was that of not being liked or accepted by others. Being popular was so important to me then, and the fear of not being liked was a serious one.
   One of the processes growing up is being able to realize and overcome our fears. Understanding the things that scared us as children helps us achieve greater success later in life.

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一元钱

    呆呆地坐在灯下,我又想起那件我永远也忘不了的小时候的事。

    六岁的是个画画(迷  谜)。因为想得到一张洁白的画纸,我偷偷拿了母亲的一元钱。那个年代,一元钱可以买许多东西。钱到手后,我仍不敢用,藏在母亲的枕下。假如母亲发现了,我就说她记错了地方;假如没发现,我就得手了。

    早上拿的,心(虚  虑)的我一整天坐在教室里感到莫名其妙的惊慌。放学的铃声还没响完,我已跑出教室——我要把钱放回原处。还未进家门,我就看见母亲阴沉着脸,手里握着根竹条等着我与哥哩。

    母亲高举竹条,(历  厉)声问我:“是你偷了那一元钱?”“偷”这个刺耳的字眼令我心惊肉跳。细细的竹条,让我看了就感到害怕。“没有!”我一口否认。

    这时,哥也回来了。一听母亲也怀疑他偷了,涨红了脸大声(辩  辨)解。

    母亲望着这对都不承认的儿女拿不定主意。女儿成绩好,又文静;儿子不用功,还特爱搞破坏活动。哥自然成了重点怀疑对象。

    竹条不由分说打在哥身上。哥流着泪,不躲不闪,哭着喊:“不是我!”

    晚上,我哪能睡得着,躲在被窝里流泪。母亲走进来,望着另一个床上熟睡的哥,自责地说:“我的手怎么这么狠?”

    我一听,越发不可收拾,泪如泉涌……我可怜的哥,怎能不明不白地替我挨打呢?我掀开被窝,低声说:“                                  

这件事虽然判断不公,但是母亲的竹条帮着我与哥健康而正直地成长。