题目

内壁光滑的环形凹槽半径为R，固定在竖直平面内，一根长度为R的轻杆，一端固定有质量为m的小球甲，另一端固定有质量为2m的小球乙，将两小球放入凹槽内，小球乙位于凹槽的最低点，如图所示．由静止释放后    A．下滑过程中甲球减少的机械能总等于乙球增加的机械能    B．下滑过程中甲球减少的重力势能总等于乙球增加的重力势能    C．甲球可沿凹槽下滑到槽的最低点    D．杆从右向左滑回时，乙球一定能回到凹槽的最低点Many Chinese students who have learnt English for more than ten years are still unable to speak English very well when they meet a foreigner. They seem to have mastered the basic language structure, but a conversation in English will make them feel uneasy. They are afraid that other people might find out their mistakes. It’s uncommon that many students who are bad speakers of English can write English perfectly. This proves that they are unable to organize their ideas in English. The center of the problem is that they lack practice and confidence(自信). Why should you be afraid? Do you fear those foreigners with whom you are speaking? Don’t be shy, they will not laugh at you just for a little mistake you make. The best way to get rid of trouble is to learn to speak by speaking more. I am sure that constant practice will help you succeed.1.What’s the best topic for the passage?A.How to speak to foreignersB.How to study English wellC.How to organize the idea in EnglishD.Practise speaking English all the time2.Many Chinese students can write English very well, but they cannot speak English freely because_______.A.they seldom meet foreignersB.they seldom practise speaking EnglishC.they had no chance to speak EnglishD.they think it’s enough to master the basic language structure3.So many Chinese students are afraid to speak to foreigners because _________.A.they are afraid they can’t understand foreignersB.they don’t think their English is poorC.they worry about making mistakes in their speakingD.they didn’t like speaking to foreigners4.According to the passenger, which of the following is NOT true?A.We can speak English fluently by doing more speaking.B.If you can write English perfectly, you are able to organize your idea in English.C.If you can write good English composition, you can speak English very well.D.Many Chinese students can’t speak English freely because they are afraid of making mistakes.