试题与答案

如图所示,L1和L2为两条平行线,L1上方和L2下方都是垂直纸面向里的磁感应强度

题型:选择题

题目:

如图所示,L1和L2为两条平行线,L1上方和L2下方都是垂直纸面向里的磁感应强度相同的足够大匀强磁场,L1与L2之间为真空区域.A、B两点都在L2上.带电粒子(不计重力)从A点以初速v与L2成θ=30°斜向上射出,粒子第一次斜向上穿过L2时,将该点标记作B点.下列判断正确的是(  )

A.粒子一定带正电

B.带电粒子经过B点时的速度一定跟在A点的速度相同

C.将带电粒子在A点时的初速度变大但方向不变,它一定不过B点

D.将带电粒子在A点时的初速度变大但方向不变,它一定 经过B点

答案:

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great   2     can be found in the smallest individuals. Let me tell you about Tyler.
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   7   to find him playing and racing around his backyard, wearing his medicineloaded backpack and  
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the window to check on him playing in the yard, she could quickly   12   him.
     This deadly disease eventually    13   down Tyler. He grew quite ill and, unfortunately,    14   did his
HIVinfected mother. When it became    15   that he wasn't going to survive, Tyler's mom talked to him
about   16  . She comforted him by telling Tyler that she was dying too, and that she would be with him
soon in heaven.
     A few days before his death, Tyler   17   to me to come to his hospital bed and    18  ,"I might die
soon. I'm not    19   . When I die, please dress me in   20  . Mom promised she's coming to heaven,
too. I'll be playing when she gets there, and I want to make sure she can find me."
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