题目

在“互成角度的两个共点力的合成”实验中，F1和F2表示两个互成角度的力，F’表示由平行四边形定则画出的合力，F表示根据“等效性”通过实验得到的合力，则图中符合实验事实的是图________。A. B. C. D. 答案：【答案】C【解析】试题分析: 实验测的弹力方向沿绳子方向，作图法得到的合力理论值在平行四边形的对角线上，由于误差的存在合力的理论值与实验值有一定的差别，故ABD错误，C正确．短文填空（每空2分，共20分）根据下列短文内容，在短文后的空格中填上一个恰当的词，使短文完整、通顺。John sent for a doctor because his wife was ill. He called the doctor and made 1.they would meet at five. He arrived at the doctor’s at twenty to five. He thought, “It’s a little 2. , I’ll wait for a moment. It’s good to keep the time.”Then he stopped his car in front of the doctor’s. He looked around and saw a noisy square not far from here. He went there and 3.down on a chair to enjoy the last light of afternoon sun and make 4.quiet. He saw some children playing and some women talking to 5.other happily.Suddenly he heard a girl crying. He came up to her and asked some questions. Then he knew she got 6.. John tried to find out her address and took her 7.. The girl’s parents were very thankful.Then John hurried to the doctor’s. The doctor said angrily 8. he saw him. “You’re late. Why did you keep me 9. for twenty minutes?” John said nothing 10.one word—“Sorry”!