如图所示,电源电动势E=60V,内阻r=1Ω,R1=3Ω,R2=6Ω.间距d=0

题型:问答题

问题:

如图所示,电源电动势E=60V,内阻r=1Ω,R1=3Ω,R2=6Ω.间距d=0.03m的两平行金属板A、B水平放置,闭合开关S,两板之间存在着匀强电场.在B板上开有两个间距为L=1.2m的小孔.M、N为两块同心1/4圆弧形金属板,圆心都在贴近B板的O′处,两板间的距离很近,两板上端的中心线正对着B板上的小孔(与B板的间隙可忽略不计),下端切线水平,P点恰好在O′的正下方,两圆弧形金属板间的电场强度可认为大小处处相等,方向都指向O′.现从正对B板小孔紧靠A板的O处由静止释放一个质量为m=1.0×10-5Kg、电量为q=1×10-3C的带正电微粒(微粒的重力不计),问:

(1)微粒穿过B板小孔时的速度多大;

(2)为了使微粒能在MN板间运动而不碰板,MN板间的电场强度大小应满足什么条件;

(3)从释放微粒开始,经过多长时间微粒通过两圆弧形金属板?

(4)为了让P点出射的带电粒子能射到B板的右侧C点小孔,现在P点外侧虚线框内另加一个竖直方向的有界匀强电场,则电场强度E为多少?

考点:向心力牛顿第二定律电场强度的定义式带电粒子在电场中运动的综合应用闭合电路欧姆定律
题型:问答题

癔症性痴呆中,对简单的问题给予近似回答,称为()

A.Ganser综合征

B.童样痴呆

C.诈病

D.病理性说谎

E.Cotard综合征

题型:问答题

Opinion polls are now beginning to show that, whoever is to blame and whatever happens from now on, high unemployment is probably here to stay. This means we shall have to find ways of sharing the available employment more widely.
But we need to go further. We must ask some fundamental questions about the future work. Should we continue to treat employment as the norm Should we not rather encourage many ways for self-respecting people to work Should we not create conditions in which many of us can work for ourselves, rather than for an employer Should we not aim to revive the household and the neighborhood, as well as the factory and the office, as centers of production and work
The industrial age has been the only period of human history in which most people’s work has taken the form of jobs. The industrial age may now be coming to an end, and some of the changes in work patterns which it brought may have to be reversed. This seems a daunting thought. But, in fact, it could offer the prospect of a better future for work. Universal employment, as its history shows, has not meant economic freedom.
Employment became widespread when the enclosures of the 17th and 18th centuries made many people dependent on paid work by depriving them of the use of the land, and thus of the means to provide a living for themselves. Then the factory system destroyed the cottage industries and removed work from people’s homes. Later, as transport improved first by rail and then by road, people commuted longer distances to their places of employment until, eventually, many people’s work lost all connection with their home lives and the places in which they live.
Meanwhile, employment put women at a disadvantage. In preindustrial times, men and women had shared the productive work of the household and village community. Now it became customary for the husband to go out to paid employment, leaving the unpaid work of the home and families to his wife. Tax and benefit regulations still assume this norm today, and restrict more flexible sharing of work roles between the sexes.
It was not only women whose work status suffered. As employment became the dominant form of work,young people and old people were excluded—a problem now,as more teenagers become frustrated at school and more retired people want to live active lives.
All this may now have to change.
The time has certainly come to switch some effort and resources away from the idealist goal crea- ting jobs for all, to the urgent practical task of helping many people to manage without full-time jobs.

It can be inferred from the passage that______.

A. most people who have been polled believe that the problem of unemployment may not be solved within a short period of time
B. many farmers lost their land when new railways and factories were being constructed
C. in preindustrial societies housework and community service were mainly carried out by women
D. some of the changes in work pattern that the industrial age brought have been reversed

题型:问答题

有A、B、C、D、E五枚邮票,其价值大小不同。

已知:

(1)A是B的两倍价值;

(2)B是C的四倍半价值;

(3)C是D的一半价值;

(4)D是E的一半价值。

那么,这五枚邮票由大到小的价值顺序是()。

A.A、E、B、D、C

B.A、B、E、C、D

C.A、B、E、D、C

D.A、E、D、B、C

题型:问答题

下列哪项不是黄连的功效()

A.清热

B.安胎

C.燥湿

D.泻火

E.解毒

题型:问答题

为了把多对多的联系分解成两个一对多联系所建立的“纽带表”中,应该包含两个表的 【6】

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