题目

两木块A，B质量分别为ｍ，M，用劲度系数为Ｋ的轻弹簧连在一起，放在水平地面上．如图所示，用外力将木块A压下一段距离静止，释放后A做简谐运动．在A的振动过程中，木块B刚好始终未离开地面，求：（1）木块A的最大加速度；（2）木块B对地面的最大压力；（3）要使B离开地面，外力至少多大？  答案：（1）am=g＋（2）Fm＝2mg＋2Mg（3）Fm=mg＋Mg解析:（1）B刚好未离开地面时，弹簧伸长量为x1，对于B，kx1=Mg对A此时，有最大加速设为am，且A应在最高点那么mg＋kx1＝mam可得：am=g＋（2）木块B对面有最大压力时，A应在最低点，此时压缩量为x2对A，kx2－mg＝mam得kx2＝2mg＋Mg对B，最大压力Fm＝kx2＋Mg＝2mg＋2Mg（3）可完形填空 先通读短文，掌握其大意，然后从A、B、C、D四个选项中选出可以一个可以填入相应空白处的最佳答案，并将其标号填入题前括号内。I still remember I fell in love with English from a very young age, because I thought it was such a(n) language. Full of strong wishes of learning English, I began to it . But soon I found it than expected. There were too many words, expressions and many other things to remember. And even if you knew , you couldn’t use them correctly and exactly. And I did rather in my first English test. I was worried about it. This made me upset(不安) and dropped my interest in English .While I was in trouble, my English teacher gave me much help. I knew that interest didn’t mean and I should have some learning methods. I did as he said and tried many different ways of learning English. the days went by, I could do better and better and became more and more interested in it.During the summer vacation, an old lady from Australia visited my school. She had a talk with us. It was the first time a foreigner. I gotnervous at first, but soon I found it exciting to talk with her, and I learned a lot from her. How I wish to practice speaking English with foreigners every day!1.A. helpful B. wonderful C. exciting D. careful2.A. read B. teach C. learn D. write3.A. better B. more difficult C. worse D. easier4.A. how to write themB. how to writeC. what to write themD. what to write5.A. well B. worse C. better D. badly6.A. one by one B. one another C. little by little D. each other7.A. everything B. anything C. nothing D. something8.A. WhenB. As C. While D. For9.A. to talk B. speakC. to meet D. meet10.A. a littleB. little C. a few D. Few