题目

如图所示，质量为M=6kg的物体处于静止状态，细绳OB与水平方向夹角为37°，细绳OA沿水平方向。求：OA、OB两根细绳的拉力大小。（取g = 10 m/s2，sin37°=0.6,cos37°=0.8）      答案：80N，100N解析:由于O点处于平衡，根据对O点进行受力分析如图所示，可得：       OA绳的拉力  （3分）      OB绳的拉力  （3分） Harry is from London. But he is in China with his parents now. He is 13 years old. He is a student of Grade 7. Harry is a clever student. He works very hard. He is good at all his lessons. He says he likes Chinese best. He can speak some Chinese now. His teachers and classmates are all nice to him. Harry gets up at 6.20 on weekdays. He has his breakfast at home. Then he walks to school. His lessons begin at 7.50 every day. In the morning, they have four classes. Harry has lunch at school with his classmates. They have three classes in the afternoon. And school is over at 4.40. After school, Harry plays ball games in the playground. He goes home at about 5.30. He has supper with his parents every day. In the evening, he does his homework and watches TV. And then he goes to bed at 9.30. “I like living in China very much. The people here are friendly and the food is very nice. I like all the things here,” He says to his parents.1.Which is Harry’s favourite subject?A.English.B.Chinese.C.Maths.D.Ball games.2.When does Harry get up in the morning?A.At 6.10.B.At 7.15.C.At 6.00.D.At 6.20.3.What does he like in China?A.The people.B.The food.C.All the things.D.We don’t know.