“滔天浊浪排空来，翻江倒海山为摧”的钱塘江大潮，被誉为天下奇

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问题计算题

“滔天浊浪排空来，翻江倒海山为摧”的钱塘江大潮，被誉为天下奇观．小莉设想用钱塘江大潮来发电，在江海交接某处建一大坝，形成一个面积为1.0×107 m，涨潮时水深达25 m的蓄水湖．，关上水闸落潮后坝内外水位差为2 m．若发电时水重力势能的12%转变为电能，并只有退潮时发电，每天涨潮两次，求该电站每天能发多少电？根据图中情景，说明图中的A、B两台机器(有一台是发电机，另一台是电动机)，哪台是发电机？(已知水的密度ρ＝1.0 ×103 kg/m3，g＝10 m/s2)

答案

4.8×1010 J　A为发电机

题目分析：退潮时水的落差是h＝2 m

水的质量是

这些水的重心下降高度

重力势能减少：

每天发出的电能为

ΔE＝2ΔEP×12%＝0.12ρSgh2＝

A为发电机．

点评：关键是要能够找到有用信息，然后根据能量守恒定律列方程求解．

阅读理解

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