题目

如图所示的几个相同单摆在不同条件下，关于它们的周期关系，其中判断正确的是 ()A. T1>T2>T3>T4B. T1<T2<T3<T4C. T1<T2＝T3<T4D. T1>T2＝T3>T4 答案：【答案】D【解析】据周期公式单摆的周期与幅和摆球质量无关，与摆长和重力加速度有关；（1）中沿斜面的加速度为a=gsinθ，所以周期为；（2）中加速度为a=g，所以周期为 （3）中的周期为 ；（4）中的加速度为a′=g+a，所以周期为；故T1＞T2=T3＞T4，故选C。At 7:40 when Mrs. Fang is at breakfast, there comes a call. Twenty minutes later, she is with Ann, because she cannot stop her baby from crying. There, Mrs. Fang helps wash Ann’s three-day-old baby and it soon becomes quiet. It is her first child and she is learning what to do. After that, Mrs. Fang goes on to see Mr. Johnson, a rich old man, he lives alone. His arm was broken and cannot wash or put on his clothes himself. He needs Mrs. Fang’s help. Then Mrs. Fang gets her second call that day. She goes to the home for the old（敬老院）. There she works with the old people till 2:00 p.m. One by one, she answers their questions and helps them take their medicine（服药）while the doctor takes care of other more serious patients（重病人）. Mrs. Fang keeps hurrying around all day and sometimes she has calls from the sick even late at night. She is busy, but she likes her job and enjoys helping others. (　 ) 6. Mrs. Fang gets her first call from _________. 　　　 A. Mr. Fang　　　　　　　　 B. Mr. Johnson　　　　　　 C. Ann　　　　　　　　 D. the sick (　 ) 7. Ann is _________. 　　　 A. a young nurse B. a new doctor　　　　　 C. Mrs. Fang’s Neighbour 　　　　　　　　　　　 D. a new mother (　 ) 8. Mrs. Fang goes to help Mr. Johnson because he is ____________. 　　　 A. rich and tall B. busy and tired 　C. old and sick D. alone but happy (　 ) 9. Mrs. Fang often stops her work in the home for the old at about _________. 　　　 A. 2:00 p.m. 　　　　　　　 B. 3:00 p.m.　　　　　　　　 C. 4:00 p.m. 　　　　 D. 5:00 p.m. (　 ) 10. From the passage we can know that Mrs. Fang ____________. 　　　 A. is a doctor B. must be a nurse in the community(社区). 　　　 C. is a teacher in a school D. must be a student