题目

如图所示 质量为M的小车放在光滑的水平而上，质量为m的物体放在小车的一端．受到水平恒力F作用后，物体由静止开始运动，设小车与物体间的摩擦力为f，车长为L，车发生的位移为S，则物体从小车一端运动到另一端时，下列说法正确的是   A、物体具有的动能为（F－f）（S+L） B、小车具有的动能为f SC、物体克服摩擦力所做的功为f (S+L)D、这一过程中小车和物体组成的系统机械能减少了f L单词拼写(共10小题;每小题1分,满分10分) 1.I have no idea of the ___________(平均) size of classes in the UK. 2.Great changes have taken place in our country ___________(近来). 3.Good ________(准备) should be made before we have the important meeting. 4.Don’t feel e__________ about being different from others. 5.I would p________ playing outdoors to watching TV at home. 6.__________ (注意力集中) more on your work or you will be fired. 7.I found it difficult to keep my b________ on the icy road. 8.She performed the most c_________ task without a mistake. 9.I’m learning German, but I still can’t speak it p_________. 10.Children should be encouraged to be i____________ thinkers.