如图所示,固定的“U”型金属框水平放置,导体棒ab与框架的两臂垂直放置,ab与框

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问题:

如图所示,固定的“U”型金属框水平放置,导体棒ab与框架的两臂垂直放置,ab与框架构成边长L的正方形回路,整个回路的电阻R=2Ω.质量m=1kg的物体c置于水平地面上,并通过轻绳绕过定滑轮与ab相连,垂直导轨方向存在竖直向l的磁场,磁场随时间变化规律为B=2t,测得物体c对地面的压力F随时间t变化的规律如图所示,不考虑一切摩擦,取g=10m/s2.求

(1)ab棒中感应电流的方向;

(2)导轨宽度L.

考点:共点力的平衡闭合电路欧姆定律磁场对通电导线的作用:安培力、左手定则法拉第电磁感应定律
题型:问答题

在矩阵型组织结构中,若项目经理向一位能给项目提供支持的高级副总裁汇报工作,则 (10) 最好地描述了该项目经理的权力。

A.在弱矩阵型组织中,权力向利益相关者倾斜

B.在强矩阵型组织中,权力向项目经理倾斜

C.在平衡矩阵型组织中.权力向项目经理倾斜

D.在平衡矩阵型组织中,权力向职能经理倾斜

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Children are a relatively modem invention. Until a few hundred years ago they look like adult, wearing grown-up clothes and grown-up expressions, performing grown-up tasks. Children did not exist because the family as we know it had not evolved.
Children today not only exist; they have taken over in no place more than in America, and at no time more than now. It is always Kids Country here. Our civilization is child-centered, child-obsessed. A kid’s body is our physical ideal. In Kids Country we do not permit middle-aged. Thirty is promoted over 50, but 30 knows that soon his time to be overtaken will come.
We are the first society in which parents expect to learn from their children. Such a topsy-turvy situation has come to abort at least in part because, unlike the rest of the world, ours is an immigrant society, and for immigrants the only hope is in the kids. In the Old Country, that is, Europe, hope was in the father, and how much wealth he could accumulate and pass along to his children. In the growth pattern of America and its ever- expanding frontier, the young man was ever advised to GO WEST; the father was ever inheriting from his son. Kids Country may be the inevitable result.
Kids Country is not at all bad. America is the greatest country in the world to grow up in because it is Kids Country. We not only wear kids clothes and eat kids food; we dream kids dreams and make them come tree. It was, after all, a boys’ game to go to the moon.
If in the old days children did not exist, it seems equally true today that adults, as a class, have begun to disappear, condemning all of us to remain boys and girls forever, jogging and doing push-ups against eternity.

By saying "condemning all of us to remain boys and girls forever, jogging and doing push-ups against eternity", the author means that ______ .

A.she thinks people shouldn’t be so concerned about physical fitness

B.she feels too old and tired to do such hard exercise

C.American society is overemphasizing youth and physical appearance

D.what happened to children centuries ago may occur to adults in America soon

题型:问答题

下列何种检查方法对肾癌诊断具有决定意义()

A.腹部平片

B.立位透视

C.选择性肾动脉造影

D.逆行肾盂造影

E.IVP

题型:问答题

按照SOLAS公约的要求,船舶应在哪些处所张贴操舵装置的遥控系统和动力装置转换程序的操作说明和方框图()。Ⅰ.驾驶室;Ⅱ.机舱;Ⅲ.舵机室;Ⅳ.引水员房间;Ⅴ.船长房间和轮机长房间。

A.Ⅱ~Ⅴ

B.Ⅰ、Ⅱ、Ⅲ、Ⅴ

C.Ⅱ~Ⅳ

D.Ⅰ~Ⅲ

题型:问答题

下列选项中,()属于发生在流体中的扩散方式。

A、对流扩散

B、分子扩散

C、涡流扩散

D、湍流扩散

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