题目

质量为m=8kg的物体，在F=12N的水平力作用下，沿光滑水平面从静止开始运动，运动时间为t=5s，试求：                                                                                              （1）力F在前4s内对物体所做的功W；                                                            （2）力F在第3s末对物体做功的功率P．                                �选择与话题词相关的单词（______）1. Spain A. Beijing B. Lechang C. China（______）2. usually A. kind B.always C. class（______）3. vacation A. Monday B. July C. holiday（______）4. a few A. a lot B. some C. things（______）5. tell A. story B. letter C. card