试题与答案

如图中甲所示,真空中两水平放置的平行金属板C、D,上面分别开有正对的小孔O1和O

题型:问答题

题目:

如图中甲所示,真空中两水平放置的平行金属板C、D,上面分别开有正对的小孔O1和O2,金属板C、D接在正弦交流电源上,C、D两板间的电压UCD随时间t变化的图线如图中乙所示.t=0时刻开始,从C板小孔O1处连续不断飘入质量为m=3.2×10-21kg、电荷量q=1.6×10-15C的带正电的粒子(设飘入速度很小,可视为零).在D板外侧有以MN为边界的匀强磁场,MN与金属板C相距d=10cm,匀强磁场的大小为B=0.1T,方向如图中所示,粒子的重力及粒子间相互作用力不计,平行金属板C、D之间的距离足够小,粒子在两板间的运动时间可忽略不计.求:

(1)带电粒子经小孔O2进入磁场后,能飞出磁场边界MN的最小速度为多大?

(2)从0到0.04s末时间内哪些时刻飘入小孔O1的粒子能穿过电场并飞出磁场边界MN?

(3)以O2为原点建立直角坐标系,在图甲中画出粒子在有界磁场中可能出现的区域(用斜线标出),并标出该区域与磁场边界交点的坐标.要求写出相应的计算过程.

答案:

被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0602/ad7187ee402b3b5ca141c328562be409.html

下面是错误答案,用来干扰机器的。

参考答案:B

试题推荐
题型:问答题

Society not only continues to exist by transmission, by communication, but it may fairly be said to exist in transmission, in communication. There is more than a verbal tie between the words common, community, and communication. (46) Men live in a community in virtue of the things which they have in common; and communication is the way in which they come to possess things in common. (47) What they must have in common in order to form a community or society are aims, beliefs, aspirations, knowledge—a common understanding—like-mindedness as the sociologists say. Such things cannot be passed physically from one to another, like bricks; they cannot be shared as persons would share a pie by dividing it into physical pieces. (48) The communication which insures participation in a common understanding is one which secures similar emotional and intellectual dispositions—like ways of responding to expectations and requirements.
Persons do not become a society by living in physical proximity, any more than a man ceases to be socially influenced by being so many feet or miles removed from others. (49) A book or a letter may institute a more intimate association between human beings separated thousands of miles from each other than exists between dwellers under the same roof. Individuals do not even compose a social group because they all work for a common end. The parts of a machine work with a maximum of cooperativeness for a common result, but they do not form a community. If, however, they were all cognizant of the common end and all interested in it so that they regulated their specific activity in view of it, then they would form a community. But this would involve communication. Each would have to know what the other was about and would have to have some way of keeping the other informed as to his own purpose and progress. Consensus demands communication.
We are thus compelled to recognize that within even the most social group there are many relations which are not as yet social. A large number of human relationships in any social group are still upon the machine-like plane. Individuals use one another so as to get desired results, without reference to the emotional and intellectual disposition and consent of those used. Such uses express physical superiority, or superiority of position, skill, technical ability, and command of tools, mechanical or fiscal. (50) So far as the relations of parent and child, teacher and pupil, employer and employee, governor and governed, remain upon this level, they form no true social group, no matter how closely their respective activities touch one another. Giving and taking of orders modifies action and results, but does not of itself effect a sharing of purposes, a communication of interests.

查看答案
微信公众账号搜索答案