如图所示,C、D为平行正对的两金属板,在D板右方一边长为l=6.0 cm的正方形

题型:计算题

问题:

如图所示,C、D为平行正对的两金属板,在D板右方一边长为l=6.0 cm的正方形区域内存在匀强磁场,该区域恰好在一对平行且正对的金属板M、N之间,M、N两板均接地,距板的右端L=12.0 cm处放置一观察屏.在C、D两板间加上如图乙所示的交变电压,并从C板O处以每秒1 000个的频率均匀的源源不断地释放出电子,所有电子的初动能均为Ek0=120 eV,初速度方向均沿OO′直线,通过电场的电子从M、N的正中间垂直射入磁场.已知电子的质量为m=9.0×10-31 kg,磁感应强度为B=6.0×10-4 T.问:

(1) 电子从D板上小孔O′点射出时,速度的最大值是多大?

(2) 电子到达观察屏(观察屏足够大)上的范围有多大?

(3) 在uCD变化的一个周期内,有多少个电子能到达观察屏?

考点:带电粒子在匀强磁场中的运动
题型:计算题

--- _____do you study for a test?

---By reading the textbook.

A.What

B.When

C.How

D.Where

题型:计算题

对工资主文件的更新是在一个实时系统中,由远程终端用户向一个主机结构程序发送。保证数据传输准确性的控制措施是:

A.回叫检测。
B.保护环。
C.杂项总和。
D.整合测试设施。

题型:计算题
I believe the best heroes are often the ones who haven’t been publicly recognized. They’re someone’s hero just by living their life as 36, not necessarily struggling for anything particular outside of survival. They’re everyday ordinary people.
37, my greatest hero without doubt isn’t a famous person or someone who has a rags-to-riches (白手起家的) story. In fact, this person isn’t a 38 at all, but a heroine: my mother, who has been my greatest source of inspiration(鼓舞).
A brief glance (一瞥) into this 39 woman’s life makes it clear. My mother was married to a man who drank like a fish almost every day. As Mother 40 to us later in life, she simply didn’t want us to be 41 by my father. So, one day she packed her seven kids into an old wagon (马车), and headed back down south to Montgomery, Alabama.
At five foot three, she was a black lady with a small figure, with no college education. She did whatever she had to do to 42 as a single(单身的) parent and to successfully 43 all her children to adulthood.
By high school I had started to 44 my mother had achieved something 45 as a single parent. Then, when I was seventeen years old, I signed up(报名) for the Marine Corps. The day I 46 for basic training, my mother told me, a very thin and nervous black kid, four 47 words: “Just do your best.” That 48 may be a cliché (套话), but coming from her , it has given me a lifetime of powerful inspiration.
I’ve had my 49 of ups and downs in my life. Whenever meeting with any difficulty, I would 50 to myself, “If Mother overcame her challenges, I have no 51 not to do the same.” 52 I grew, I admired her for what she had achieved.
I graduated from community college with highest 53, and now I’m a student at Columbia University. Every step of the 54, I’ve been encouraged by the inspiration of my mother — my heroine. I’ve never 55. I’ve tried to do my best. 
小题1:
A.muchB.usual C.well D.active
小题2:
A.IndeedB.OtherwiseC.ThereforeD.Altogether
小题3:
A.heroB.modelC.heroineD.example
小题4:
A.educatedB.famousC.generous D.unusual
小题5:
A.explainedB.repliedC.devotedD.responded
小题6:
A.employedB.fooledC.influencedD.missed
小题7:
A.escapeB.surviveC.hide D.recover
小题8:
A.raiseB.addC.enrich D.attract
小题9:
A.believeB.imagineC.determineD.realize
小题10:
A.excitingB.interestingC.tiringD.amazing
小题11:
A.waitedB.returned C.leftD.came
小题12:
A.honestB.simpleC.uselessD.extra
小题13:
A.answerB.praiseC.expressionD.encouragement
小题14:
A.movementB.experiencesC.originD.advantage
小题15:
A.thinkB.lieC.reactD.object
小题16:
A.demand B.abilityC.causeD.excuse
小题17:
A.As B.ThoughC.UnlessD.Before
小题18:
A.honorsB.flameC.pressure D.purpose
小题19:
A.escapeB.dangerC.wayD.hope
小题20:
A.appearedB.stopped C.knocked D.glanced
题型:计算题

产权理论的基本框架包括交易费用理论、产权效率分析、产权制度的选择与调整及产权制度的演进。

题型:计算题

治疗胁肋胀痛,暖气吞酸,舌红苔薄黄,脉弦数者。宜选用

A.枳实
B.陈皮
C.木香
D.香附
E.川楝子

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