题目

如图所示，一个质量为0.6kg的小球以某一初速度从P点水平抛出，恰好从光滑圆弧ABC的A点的切线方向进入圆弧（不计空气阻力。进入圆弧时无机械能损失）。已知圆弧的半径R=0.3m，θ=60°。小球到达A点时的速度v=4m/s。（g取10m/s2）试求：(1)小球做平抛运动的初速度；(2)P点与A点的水平距离和竖直高度； 答案：【答案】(1)2m/s；(2)0.6m； 0.69m【解析】(1)小球到A点的速度如图所示由图可知=2m/s(2)由平抛运动规律得竖直方向有m/s水平方向有解得h=0.6m假如英语课上老师要求同学们交换修改作文，请你修改你同桌写的一篇作文。文中共有10处语言错误， 要求你在错误的地方增加、删除或修改某个单词。 增加：在缺词处加一个漏字符号（∧），在其下面写上该加的词。 删除：把多余的词用斜线（\）划掉。 修改：在错的词下划一横线，并在该词下面写上修改后的词。 注意：1.  每处错误及其修改均仅限一词； 2．只允许修改10处，多者（从11处起）不记分。 例如：It was very nice to get invitation to spend ∧ weekend with you. Luckily                                                             the ﹨   I was completely free then, so I’ll to say “yes”. I’ll arrive in Bristol at around 8 pm in Friday evening.   am                                                              on On Monday morning, I was on my way to school when suddenly as I saw a boy knocked down by the car. In a hurry, I ran over and found the boy was serious hurt with much blood on his face. Immediately, I call an ambulance and the boy was taken to the nearest hospital. For my relief, the boy was fine and would recover in a few day. I went away without leaving his name. I was late for class, and I felt happy for what I had done. As a proverb says, “Help others is the source of happiness.” I feel our duty to make the world a better place to live in.