如图所示，在水平地面上方A点处有一小球a距地面20m，在B点处有另一个小球b距地面15m，两小球均做自由落体运动，但a比b提前1s释放，g取l0m/s2，两小球均可视为质点．则（ ）
A．在下落过程中，a、b两小球“相遇”点恰好在B点
B．在下落过程中，a、b两小球“相遇”点发生在B点以下某位置
C．a、b两小球同时到达地面
D．a小球先到达地面
A、由于a比b提前1s释放，故a在1s内下落的位移为：h1=
gt12=1 2
×10×1=5m，因为a在b上方5m处，故a到B处时候b才开始释放，故a、b两小球相遇点恰好在B处，故A正确，B错误；1 2
C、由于在B点相遇时a有初速度，b没有，故a先落地，b后落体．故C错误，D正确．
故选：AD．
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| We were late as usual. My husband had insisted on watering the flowers in the garden by him self, and 1 he discovered that he couldn't manage he asked me for 2 at the last moment. So now we had only an hour to get to the airport. Luckily there were not many cars and buses on the road and we were 3 to get there just in time. We checked in and went straight into a big hall to wait for our 4 to be called. We waited and waited 5 no announcement was made.We asked for 6 and the girl there told us that the 7 hadn't arrived yet. In the end there came an announcement telling us that those 8 for Flight JJ 108 could get a free meal voucher (代金卷) and that the plane hadn't left Spain 9 technical problems. We thought that meant that it was not 10 for the plane to 11. We waited again for a long time until half 12 when we were asked to report again. This time we were given free vouchers to spend the night in a 13 hotel. The next morning after a 14 night because of all the planes 15 off and landing, we were reported back to the airport. Guess 16 had happened while we were 17. Our plane had arrived and taken off again. All the other 18 had been woken up in the night to 19 the plane, but for some reason or other we had been 20. You can imagine how we felt. | |||
| ( ) 1．A. when ( ) 2．A. food ( ) 3．A. impossible ( ) 4．A. plane ( ) 5．A. so ( ) 6．A. time ( ) 7．A. policeman ( ) 8．A. coming ( ) 9．A. for ( )10．A. possible ( )11．A. repair ( )12．A. evening ( )13．A. faraway ( )14．A. bad ( )15．A. turning ( )16．A. what ( )17．A. awake ( )18．A. workers ( )19．A. get ( )20．A. woken | B. before B. advice B. necessary B. flight B. but B. advice B. plane B. sitting B. since B. important B. sell B. noon B. nearby B. quiet B. putting B. where B. asleep B. planes B. catch B. announced | C. while C. praise C. able C. fly C. otherwise C. help C. driver C. waiting C. because C. safe C. fly C. morning C. distant C. sweet C. taking C. it C. alone C. passengers C. drive C. lost | D. until D. help D. unable D. flying D. if D. information D.train D. working D. from D. difficult D. telephone D. afternoon D. silent D. pleasant D. keeping D. that D. afraid D. flights D. ride D. forgotten |