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问题 选择题

关于匀变速直线运动的公式，有下面几种说法，正确的是（　　）

A．由公式a=（vt-v0）/t可知，做匀变速直线运动的物体，其加速度a的大小与物体运动的速度改变量（vt-v0）成正比，与速度改变量所对应的时间t成反比

B．由公式a=（vt2-v02）/2s可知，做匀变速直线运动的物体，其加速度a的大小与物体运动的速度平方的改变量（vt2-v02）成正比，与物体运动的位移s成反比

C．由公式s=at2/2可知，做初速度为零的匀变速直线运动的物体，其位移s的大小与物体运动的时间t的平方成正比

D．由公式vt=vo+at可知，做匀变速直线运动的物体，若加速度a＞0，则物体做加速运动，若加速度a＜0，则物体做减速运动

答案

A、物体做匀变速直线运动，加速度保持不变，根据a=

vt-v0
t
，其为加速度的定义式，不能说加速度a的大小与物体运动的速度改变量（vt-v0）成正比，与速度改变量所对应的时间t成反比错误；

B、物体做匀变速直线运动，加速度保持不变，其加速度a的大小与物体运动的速度平方的改变量（vt2-v02）成正比，与物体运动的位移s成反比错误；

C、因为匀变速直线运动的加速度保持不变，故根据=at2/2可知，做初速度为零的匀变速直线运动的物体，其位移s的大小与物体运动的时间t的平方成正比正确；

D、物体做加速运动还是减速运动根据物体运动的速度方向与加速度方向是否相同决定，同向为加速反向为减速，由公式vt=vo+at可知，做匀变速直线运动的物体，取初速度方向为正方向，则若加速度a＞0，则物体做加速运动，若加速度a＜0，则物体做减速运动；困本题中没有注明速度方向为正，仅根据加速度的方向判断加速还是减速是错误的．

故本题选C．

多项选择题

肾结核合并对侧肾积水的原因（）。

A.对侧肾结核

B.对侧输尿管结核

C.对侧输尿管口狭窄

D.对侧输尿管口关闭不全

E.膀胱挛缩
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单项选择题

The question of what children learn and how they should learn it is continually being debated and redebated. Nobody dares any longer to defend the old system, the learning of lessons parrot-fashion and the grammar with-a-whip system, which was good enough for our grandparents. The theorists of modem psychology have stepped in to argue that we must understand the needs of children. Children are not just small adults; they are children who must be respected as such.
Well, you may say, this is as it should be, and a good idea. But think further. What happens "Education" becomes the responsibility not of teachers, but of psychologists. What happens then Teachers worry too much about the psychological implications of their lessons, and forget about the subjects themselves. If a child dislikes a lesson, the teacher feels that it is his fault, not the child’s. So teachers worry whether history is "relevant" to modem young children. And do they dare to recount stories about violent battles Or will this make the children themselves violent Can they tell their classes about children of different races, or will this encourage racial hatred Why teach children to write grammatical sentences Verbal expression is better. Sums Arithmetic No, no; real-life mathematical situations are more understandable.
You see you can go too far. Influenced by educational theorists, who have nothing better to do than write books about their ideas, teachers leave their teacher-training colleges filled with grand, psychological ideas about children and their needs. They make elaborate, sophisticated preparations and try out their "modem methods" on the long-suffering children. Since one "modem method" rapidly replaces another, the poor kids will have had a good bellyful by the time they leave school. Frequently the modem methods are so sophisticated that they fail to be understood by the teachers, let alone the children; even more often, the relaxed discipline, so essential for the "informal" feeling the class must have, prevents all but a handful of children from learning anything.

What do the modem psychologists maintain

A．Children must be understood and respected.

B．Children are small adults and know what they need.

C．Children are better off without learning lessons.

D．Education of children is the responsibility of psychologists.
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