题目

在做“研究匀变速直线运动”的实验时，所用电源频率为50Hz，取下一段纸带研究，如图，设0点为计数点的起点，每两个计数点间有四个实际点未画出，则第一个计数点1与起点0间的距离x1=___________cm，计算此纸带的加速度大小a=___________m/s2；物体经过计数点2的瞬时速度为v2=___________m/s。 答案：【答案】3 3 0.75 【解析】[1]由匀变速直线运动中，任意连续相等的时间间隔内位移差恒定，即有其中x2=6cm，x3=15cm-6cm=9cm代入可得x1=3cm[2]由于每两个计数点间有四个实际点未标出，则每两个计数点的时间间隔T=5×0.02s=0.1s，此纸带的加速度大小为[3]由中间时刻的瞬时速度等于这段时间内的平均速度可知，物阅读理解One morning, it was already a quarter to eight when I got up. I was afraid that I would be late so I put on my clothes hurriedly and left without breakfast.There were so many people at the bus stop that it was not easy to catch a bus. Five minutes went by, I still couldn't get on one. The only thing I could do was to walk. I rushed through the crowded and ran towards my school. Unexpectedly, I hit an old woman, and she fell down. Without saying sorry, I left her and went on my way.That evening, when I was back from school, I learned that the old woman was badly hurt in the leg from the fall. Some kind people sent her to a hospital after I left. I felt very sorry and nearly cried. The only way for me to ask her pardon was to pay her a visit.The next day, I went to the hospital, I met the old woman and told her who I was. At first I thought that she would give me . To my surprise, she didn't, but smiled. For me, that smile was worse. She touched my hand and said, “Never mind, my girl, I knew you didn't want to hurt me, did you? Don't worry, I will be better soon.”（1）The writer had to walk to school because .A.he got up earlyB.he hit the woman the busC.the bus was lateD.it was difficult to get on（2）What happened to the old woman after her fall?A.her leg was badly hurtB.She was all rightC.She scolded the writerD.The writer sent her to a hospital.（3）The underlined phrase “a scolding” means some.A.cold eyesB.bad wordsC.warm smileD.useful money（4）From the passage, we know that.A.The writer might be a manager in a companyB.The writer wanted to hit the old woman.C.The old woman understand the writer very well.D.The old woman was probably ill at home.