探究“阻力对物体运动的影响”的实验装置如图所示．
（1）实验时，每次必须使小车从斜面的同一高度滑下，这样做的目的是______；
（2）下表是一组同学记录的实验数据，分析表中内容可知：水平面越光滑，小车受到的阻力越______，小车前进的距离就越______；
| 接触面 | 毛巾 | 棉布 | 木板 |
| 阻力的大小 | 大 | 较大 | 较小 |
| 小车移动的距离s/cm | 18.3 | 22.6 | 26.7 |
（1）让小车每次从斜面的同一高度由静止开始滑下，这样做是为了使小车到达水平面时的机械能相同，速度相同；
故答案为：让小车具有相同的初速度．
（2）毛巾、棉布、木板依次越来越光滑，阻力也越来越小，从小车前进的距离来看，阻力越小，小车运动的距离越远；
故答案为：小；远．
（3）当秋千运动到最高点时，人和秋千在这一瞬间是静止的，所以当此时外力全部消失时，人和秋千都会保持静止的状态不再改变，故只有选项A符合题意．
故答案为：A．
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| Once there was a king who liked pictures very much. One day, he 1 a prize to the artist who would paint the best picture of peace. Many artists 2 . The king looked at all the pictures. But there were only two he 3 liked, and he had to choose between them. One picture was of a calm lake. The lake was a perfect 4 for peaceful towering mountains all around it. 5 was a blue sky with fluffy (蓬松的) white clouds. All who saw this 6 thought that it was a perfect picture of peace. 7 picture had mountains, too. But these were large, rough and 8 . Above was an angry sky, from which rain fell and in which lightning 9 . Down the side of the mountain 10 a foaming (起泡沫的) waterfall. This did not look 11 at all. But when the king looked 12 , he saw behind the waterfall a tiny 13 growing in a crack in the rock. In the bush a mother bird had built her 14 . There, in the midst of the rush of angry water, sat the mother bird on her nest- 15 perfect peace. Which picture do you think won the prize? The king 16 the second picture. Do you know why? "Because," 17 the king, "peace does not mean to be in a place 18 there is no noise, trouble, or hard work. Peace means to be in the midst of all those things and 19 be calm in your heart. That is the real 20 of peace." | ||||
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