问题
选择题
| 如图所示，在x轴上方存在着垂直于纸面向里、磁感应强度为B的匀强磁场，一个不计重力的带电粒子从坐标原点O处以速度v进入磁场，粒子进人磁场时的速度方向垂直于磁场且与x轴正方向成120°角，若粒子穿过y轴正半轴后在磁场中到x轴的最大距离为a，则该粒子的比荷和所带电荷的正负是（ ） A． B． C． D．  |
，正电荷
，正电荷
，负电荷
，负电荷
答案
答案：C
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| 如图所示，在x轴上方存在着垂直于纸面向里、磁感应强度为B的匀强磁场，一个不计重力的带电粒子从坐标原点O处以速度v进入磁场，粒子进人磁场时的速度方向垂直于磁场且与x轴正方向成120°角，若粒子穿过y轴正半轴后在磁场中到x轴的最大距离为a，则该粒子的比荷和所带电荷的正负是（ ） A． B． C． D． |
答案：C
| Reading comprehension. | |
| I've got some information for everyone going to Britain next month. As you know, you'll be staying with a family for two weeks. Now the most important thing is money. You should take about ￡30 in cash (现金) and about ￡200 in traveler cheques (支票). Then when you arrive at the airport you'll be met by our host (主人) family. You must remember to wear a red shirt so the family will find you easily. I've told them to look out for the red shirts. You'll also need to take with you 4 photos of yourself and, of course, it's very important that you take the school letter. While you are there, if you have any problems, you can call our agent. I'll give you her office phone number now. it's 580-4436 and the person to ask for is Mrs. Belcher, that's B-E-L-C-H-E-R. She's in the office from 9:00 a.m -5: 00 p.m. every day. OK! That's everything. Have a good trip. | |
Fill in each blank according to the passage. (根据短文内容填空, 词数不限)
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