如图所示是小伟踢足球的情景，下列分析正确的是
A．踢球时，球对脚没有作用力
B．球在空中飞行仍受到脚的作用力
C．球在空中做抛物线（曲线）运动，所受的合力为0
D．球在地面越滚越慢是由于受到阻力
答案：D
题目分析：A．根据力的作用相互的原理，踢球时，球对脚有作用力，故A错误；
B．球在空中飞行是由于惯性，不再受到脚的作用力，故B错误；
C．球在空中做抛物线（曲线）运动，不是平衡状态，所受的合力不为0，故C错误；
D．根据力和运动的关系，力是改变物体运动状态的原因，球在地面越滚越慢是由于受到阻力作用，故D正确。
故选D。
点评：关键是合力为零时，受力为平衡力，物体应处于平衡状态，另外知道力的作用相互性。
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| The school was across the street from our home and I would often watch the kids as they played during the break. She seemed so small as she pushed her way 1 the crowd of boys on the playground. She 2 from them all. I began to notice her at other times, basketball in hand, playing 3 . She would practice dribbling (运球) and shooting over and over again, sometimes until 4 . One day I asked her 5 she practiced so much. She looked 6 in my eyes and without a moment of hesitation she said, "I want to go to college. The only way I can 7 is if I get a scholarship. I am going to play college basketball. I want to be 8 . My Daddy told me if the dream is big enough, the facts don't count." Well, I had to give it in to her-she was 9 . One day, I saw her sitting in the grass, head 10 in her arms. I walked toward her and quietly asked what was 11 . "Oh, nothing," came a soft reply. "I am just too short." The coach told her that at her height she would probably 12 get to play for a top ranked team, 13 offered a scholarship. So she 14 stop dreaming about college. She was 15 and I sensed her disappointment. I asked her if she had talked to her dad about it yet. She told me that her father said those coaches were wrong. They just did not 16 the power of a dream. He told her 17 she really wanted to play for a good college, if she truly wanted a scholarship, 18 could stop her except one thing-her own attitude. He told her again, "If the dream is big enough,the facts don@^@^@t count." The next year, as she and her team went to the Northern California Championship game, she was seen by a college recruiter (招聘人员). She was indeed offered a 19 . She was going to get the college education that she had 20 and worked toward it for all those years. | ||||
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