（12分）如图（a）所示, 水平放置的平行金属板AB间的距离d=0.1m_爱下问搜题

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问题计算题

（12分）如图（a）所示, 水平放置的平行金属板AB间的距离d=0.1m，板长L=0.3m,在金属板的左端竖直放置一带有小孔的挡板,小孔恰好位于AB板的正中间.距金属板右端x=0.5m处竖直放置一足够大的荧光屏．现在AB板间加如图（b）所示的方波形电压，已知U₀=1.0×10²V．在挡板的左侧，有大量带正电的相同粒子以平行于金属板方向的速度持续射向挡板，粒子的质量m=1.0×10^-7kg，电荷量q=1.0×10^-2C，速度大小均为v₀=1.0×10⁴m/s．带电粒子的重力不计．

求：（1）在t=0时刻进入的粒子，射出电场时竖直方向的速度；

（2）荧光屏上出现的光带长度；

（3）若撤去挡板，同时将粒子的速度均变为v=2.0×10⁴m/s，则荧光屏上出现的光带又为多长?

答案

（1）10³ m/s （2）4.0×10^-2m （3）0.15m

题目分析：（1）从t=0时刻进入的带电粒子水平方向速度不变。

在电场中运动时间t=L/v₀=3×10^-5s ，正好等于一个周期（1分）

竖直方向先加速后减速，加速度大小（1分）

射出电场时竖直方向的速度（1分）

（2）无论何时进入电场，粒子射出电场时的速度均相同。

偏转最大的粒子偏转量（2分）

反方向最大偏转量（2分）

形成光带的总长度l=4.0×10^-2m （1分）

（3）带电粒子在电场中运动的时间为T/2，打在荧光屏上的范围如图c所示。

（1分）

（1分）

形成的光带长度l=d₁+ d+ d₂=0.15m （2分）

多项选择题

下列选项中属于我国社会法部门的有（）。

A. * * 法

B.知识产权法

C.劳动合同法

D.法院组织法

完形填空

阅读下面短文，掌握其大意，然后从16--35各题所给的四个选项A、B、C、D中，选出最佳选项。
To develop her students' spelling skills, Mrs Hardy held a spelling competition in her class．The two 16 spellers would compete in the school spelling competition with other 17 from the fourth, fifth and sixth grades．
Spelling was Jasmine's 18 subject and books were her best friends． 19 would allow her to 20 into the sea, find buried treasure, 21 meet the mean man Mr Grandet（葛朗台）．Fairy tales 22 her to dream of being a princess．
The day came for Mrs Hardy to 23 the result of the competition．Jasmine sat in her seat．Finally Mrs Hardy announced that Reece Bradley and Jasmine Russell would 24 in the school final spelling competition．
Smiling 25 , Jasmine looked at Reece, but he 26 her by frowning（皱眉） as if he were 27 to take part in the competition．
“Way to go, Jasmine,” Rashad, Jasmine's another classmate, said with a playful push to her arm．“Do you think you have a 28 of winning the competition?”
Jasmine 29 , “My Aunt Lucy says anything can be got by 30 hard．I'm going to study the word list till my 31 stop working!”
During the break, Jasmine, Rashad and Reece met on the basketball court for a game of Horse．Jasmine said, “Let's 32 for the competition by spelling bigger words!”
“Like what?” Rashad asked．Jasmine smiled．“Like antidisestablishmentarianism．” Reece rolled his eyes and asked．“Anti—what?”
Jasmine 33 the word, trying not to laugh．“You made that 34 ,” Rashad said．“Anything can be got by working hard．This is__ 35 everybody should believe in．

A．competitors