质量为m的物块A,置于与水平面成角的斜面B上,如图所示。A与B间的摩擦系数为f,为保

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问题:

质量为m的物块A,置于与水平面成角的斜面B上,如图所示。A与B间的摩擦系数为f,为保持A与B一起以加速度a水平向右运动,则所需的加速度至少是()。

A.

B.

C.

D.

考点:注册土木工程师水利水电工程2013土木工程师(水利水电工程师)基础知识考试真题及答案
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It is natural for young people to be critical of their parents at times and to blame them for most of the misunderstandings between them. They have always complained, more or less justly, that their parents are out of touch with modem ways; that they are possessive and dominant; that they do not trust their children to deal with crises; that they talk too much about certain problem—and that they lack sense of humor, at least in parent-child relationships.

I think it is true that parents often underestimate their teenage children and also forget how they themselves felt when young.

Young people often irritate their parents with their choices in clothes and hairstyles, in entertainers and music. This is not their motive. They feel cut off from the adult world into which they have not yet been accepted. So they create a culture and society of their own. Then, if it turns out that their music or entertainers or vocabulary or clothes or hairstyles irritate their parents, this gives them additional enjoyment. They feel they are superior, at least in a small way, and that they are leaders in style and taste.

Sometimes you are resistant and proud because you do not want your parents to approve of what you do. If they approve, it looks as if you are betraying your own age group. But in that case, you are assuming that you are the underdog; you cannot win but at least you keep your honor. This is a passive way of looking at things. It is natural enough after long years of childhood, when you were completely under your parents’ control. But it ignores the fact that you are now beginning to be responsible for yourself.

If you plan to control your life, cooperation can be part of that plan. You can charm others, especially your parents, into doing things the way you want. You can impress others with your sense of responsibility and initiative, so that they will give you the authority to do what you want to do.

Teenagers do not want their parents to approve of whatever they do because they ().

A. have already been accepted into the adult world

B. feel that they are superior in a small way to the adults

C. are not likely to win over the adults

D. have a desire to be independent

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焦点为F1(-4,0)和F2(4,0),离心率为2的双曲线的方程是

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汽车的总质量是由哪几部分组成?()

A.整备质量

B.允许最大载重量

C.驾驶员质量

D.随员质量

题型:单项选择题

从智者学派到亚里士多德,哲学思想发展的相同点是()

A.对自然界本身的探讨和解释

B.以人为本、洞察宇宙、探索人生

C.否定神或命运等超自然的力量对社会人生的作用

D.放弃对自然的探讨而去研究人自身。

题型:单项选择题

传染性造血器官坏死病毒主要侵害的鱼类是()

A.草鱼

B.虹鳟

C.鲤

D.罗非鱼

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