问题
不定项选择
质量为2kg的物体在光滑水平面上受到与水平方向成30°角的拉力F=3N的作用，经过10s（取g=10m/s2） [ ]
A．力F的冲量为30N·s
B．物体的动量的变化是30kg·m/s
C．重力的冲量是零
D．弹力的冲量是18N·s
答案
A
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质量为2kg的物体在光滑水平面上受到与水平方向成30°角的拉力F=3N的作用，经过10s（取g=10m/s2） [ ]
A．力F的冲量为30N·s
B．物体的动量的变化是30kg·m/s
C．重力的冲量是零
D．弹力的冲量是18N·s
A
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| A few days ago I got on a bus and took a window seat. The bus 1 was by the seashore and I was watching the sea waves. After a few minutes the bus got to the next 2 . A boy and a girl got on the bus. They were 3 when the bus took off. I glanced at them curiously and realized all the window 4 were occupied. They could have sat down but not together. Suddenly a(n) 5 passed through my mind. I 6 and offered them my seat. The young lady 7 and said, "Thank you very much." Then we 8 ways after I moved to another seat. I don't 9 whether I got off the bus before them or not. Months passed by. One day I was standing at the same bus stop when I heard a 10 , "Excuse me, Uncle." I glanced in the 11 of it. It was a beautiful young charming girl. Puzzled, I said, "I don't think I 12 you." She said, "But I do. Do you remember you gave up your window seat?" I said, "Maybe, but what is so 13 in that?" She said, "Uncle, you simply 14 like God for me. If you hadn't given up your seat that day, I wouldn't have sat with my friend. Our sitting 15 helped us bridge a misunderstanding that had been 16 us. Do you know we are getting 17 at the end of next month?" " 18 ! God bless both of you," I replied. The young lady thanked me again and went on with her 19 . I realized the importance of giving that day. I also found that small things could 20 great happenings in life. | ||||
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