题目

重力的作用点叫__________．物体的重心可以通过悬挂法、支撑法等来确定．均匀、规则物体的重心在它的几何中心（不一定在物体上）． 答案：【答案】重心【解析】重心是物体所受重力的作用点．质量分布均匀、形状规则的物体的重心不一定在物体上。只有薄形物体的重心可以悬挂法确定，其他物体的重心无法用悬挂法确定重心。重力的作用点叫重心，重心是物体所受重力的合力的作用点；质量分布均匀、形状规则的物体的重心一定在物体Mr. Jones had a nice brown coat. He loved it very much, but his wife didn’t like it. Because it was old. She often said. “Give it to a poor man.” But Mr. Jones always answered, “No, I like this coat.”Then a cigarette（香烟 ）fell on it and made a hole in it. So Mrs. Jones said, “Please don’t wear it again.” Mr. Jones took it to a small tailor（裁缝） “Please make another coat like this one.” The tailor made the coat very carefully. Then he lit （点燃）a cigarette, and made a hole in it in the same place.1.Mrs. Jones didn’t like the coat because .A. it was nice and brown B. it was not nice C. it was very old D. it was not old2.Mr. Jones always said, “ ”.A. I like this coat B. Give it to a poor manC. No, I don’t like this coat. D. I don’t give it to a poor man3.Mr. Jones asked the tailor to .A. make a new hole in the coat B. make a new coatC. make a hole in the new coat D. make more money4.Who do you think was foolish?A. The tailor B. Mr. Jones C. Mrs. Jones D. Nobody