题目

下列说法正确的是（    ） A.功是矢量，其正负号表示方向 B.功是标量，正、负表示外力对物体做功，还是物体克服外力做功 C.力对物体做正功还是做负功，取决于力和位移方向的夹角 D.力做功总是在某过程中完成的，所以功是一个过程量 答案：BCD 解析:功是标量，其正负号，不表示大小，也不表示方向，只表示做功的力是动力还是阻力.由W=Fscosα知，功的正负由夹角α决定.力做负功，通常说成物体克服这个力做功.B、C、D正确.短文改错（共10小题;每小题1分，满分10分）假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句最多有两处，每处错误仅涉及一个单词的增加、删除或修改。增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。删除：把多余的词用斜线（\）划掉。修改：在错的词下划一横线，并在该词下面写出修改后的词。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（从第11处起）不计分。 I saw an accident happened on my way to home this afternoon. A girl was crossing the street on a zebra crossing while a young man drove a motorbike towards her. The young man saw the girl and tried to stop, and he drove too fast to stop. He hit the girl and fell off her motorbike. The girl was badly hurt and couldn’t move. The young man didn’t know how to do. I ran to a phone box nearby and dialed 110. Soon the police reached. They sent her hospital at once. One of the policeman talked to the young man and wrote something down while was talking. I think it is very dangerous to drive very fast.