如图所示．一足够长的固定斜面与水平面的夹角为370，物体A以初速度V1从斜面顶端水平抛出，物体B在斜面上距顶端L＝15m处同时以速度V2沿斜面向下匀速运动，经历时间t物体A和物体B在斜面上相遇，则下列各组速度和时间中满足条件的是（sin37O＝0．6，cos370＝0．8，g＝10 m/s2）
A．V1＝16 m/s，V2＝15 m/s，t＝3s．
B．V1＝16 m/s，V2＝16 m/s，t＝2s．
C．V1＝20 m/s，V2＝20 m/s，t＝3s．
D．V1＝20m/s，V2＝16 m/s，t＝2s．
答案：C
解由平抛运动规律可知，tanθ＝
，将θ=37°代入解得： 3v1=20t，故只有C选项满足条件。
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| In the early 1800's, a boy named John lived in an orphanage (孤儿院) with several other children. Every day was 1 working and Christmas was the one day of the year 2 the children did not work and received a gift - an orange. The children 3 it so much that they kept it for weeks, and even 4 -smelling it, 5 it and loving it. Usually they tried to preserve (保护) it for so 6 that it often went bad before they ate it. This year John knew he would soon be 7 enough to leave. He would save the orange until his birthday in July. If he preserved it 8 , he might be able to eat it on his birthday. Christmas day finally came. The children were so 9 as they entered the dining hall. In his excitement, John knocked over something, causing a big 10 . Immediately the master shouted, "John, leave the hall and there will be no orange for you." John's heart 11 . He turned and ran back to the 12 room so that the children wouldn't see his tears. Then he heard the door open and the children entered. Little Elizabeth with a 13 on her face held out her small hands. "Here John," she said, "this is for you." As John 14 his head, he saw a big juicy 15 all peeled and quartered … Each child had sacrificed (舍弃) their own orange by 16 a quarter and had created a big, beautiful orange for him. John never forgot the sharing, love and personal 17 his friends had shown him that Christmas day. 18 that day, after he became rich, every year he 19 send oranges all over the world to children everywhere. His 20 was that no child would ever spend Christmas without a special Christmas fruit! | ||||
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