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来源：学生作业帮助网 编辑：作业帮 时间：2024/04/28 01:27:18

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1.观察着站在列车第一节车厢前端一侧地面上,列车从静止开始做匀速直线运动,测得第一节车厢通过他用了4s,列车全部通过用了20s,（1）这列车一共有几节车厢组成（车厢等长且不计车相间距离）?（2）最后九节车厢经过他身旁的时间为多少?
2.已知冰的密度=0.9*10^3kg/m^3,体积为36立方分米的水结成冰,则冰的体积是多少平方米.
3.实验室常测某种物质密度的原理是________,依据这个原理,在测某种液体密度时,如果先用量筒测其体积,然后再用天平测其质量,则测出的实际值比真实值要________.
4.拉力与摩擦力是平衡力吗?（匀速直线运动）
那么 16N 的力可以让 小车 匀速直线运动 摩擦力是16N吗?
用22N的力 能让 这个小车 匀速直线运动吗?
5.拦河大坝使上游的水位升高,提高水的势能.水从大坝的上游流下时冲击水轮机,水的势能最终转化为电能.
瑞士的大笛克桑斯大坝高284m,我过葛洲坝水电站的拦河大坝高70m.有人说前者水的重力势能比后者的大,能够这样简单地得出结论吗?为什么?

我觉得好

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