题目

 (10分)如图所示的电路中，两平行金属板A、B水平放置，两板间的距离d=40Cm．电源电动势E=24V内电阻r=l，电阻R=15闭合开关S，待电路稳定后，将一带正电的小球从B板小孔以初速度v0=4m/s竖直向上射入板间。若小球带电量为q=1×10-2C，质量为m=2×10-2kg，不考虑空气阻力那么，滑动变阻器接入电路的阻值为多大时，小球恰能到达A板?此时，电源的输出功率是多大?（取g 10m/s2）   听力理解 第一节(共5小题；每小题1.5分，共7.5分) 听下面5段对话。每段对话后有一道小题，从每题所给的A、B、C三个选项中选出最佳选项。听完每段对话后，你将有10秒钟的时间来回答有关小题和阅读下一小题。每段对话你将听一遍。 1．What book has the woman bought? A．A history book． B．A book for a music course． C．An English book． 2．How far is the post office? A．Four blocks away． B．Five blocks away． C．Six blocks away． 3．What can we learn about Mr．Robert? A．He is strange． B．He is excellent． C．He is rich． 4．What are the two speakers going to do? A．Stay at home． B．Go to the mountains． C．Go to the beach． 5．Where will the woman go first? A．Pizza Hut． B．The library． C．The supermarket． 第二节(共15小题；每小题1.5分，共22.5分) 听下面6段对话或独白。每段对话或独白后有几道小题，从每题所给的A、B、C三个选项中选出最佳选项。听每段对话或独白前，你将有5秒钟的时间阅读每小题。听完后，每小题给出5秒的作答时间。每段对话或独白你将听两遍。 听第6段材料，回答第6至7题。 6．Where did the woman live before? A．In Perth． B．In Sydney． C．In a small town． 7．What’s the weather like there in summer? A．It’s nice but windy． B．It’s nice but wet． C．It’s windy and wet． 听第7段材料，回答第8至9题。 8．Where does this conversation most likely take place? A．At a video shop． B．At a cinema． C．At a language lab． 9．How much is the rent for new movies? A．＄2． B．＄6． C．＄3.50． 听第8段材料，回答第10至11题。 10．What are the speakers mainly talking about? A．Studying abroad． B．Economic independence． C．Relationships with parents． 11．What does the man think of his parents? A．They control him too much． B．They never express love to him． C．They are easy to get along with． 听第9段材料，回答第12至14题。 12．What’s the relationship between the two speakers? A．Workmates． B．Schoolmates． C．Teacher and student． 13．Why did Jeanie come here earlier? A．To meet her friend． B．To have her class． C．To review for the test． 14．What’s Jack’s attitude toward the test? A．He is confident． B．He worries about it． C．He has to get an A． 听第10段材料，回答第15至17题。 15．When does the man usually watch TV? A．At 11 p.m.and at midnight． B．Around breakfast and at midnight． C．In the morning and in the afternoon． 16．What does the man expect to see on the new channel? A．News and commercials． B．Local service programs． C．Old comedy shows． 17．What is the woman doing? A．Asking for advice． B．Offering Information． C．Making suggestions． 听第11段材料，回答第18至20题。 18．How do the cheerleaders perform their jobs? A．They set off fireworks． B．They put on athletic shows． C．They run around the crowds． 19．Why do the cheerleaders sometimes suffer physical injuries? A．Because they shout and yell． B．Because they dance too much． C．Because they try dangerous acts． 20．What can we learn from the speech? A．Cheerleading is just for fun． B．Cheerleaders have monthly contests． C．Cheerleading is something like sports．