如图所示，在倾角为37°的固定斜面上静置一个质量为5kg的物体，物体与斜面间的动摩擦因数为0.8．sin 37°=0.6，cos 37°=0.8．求：

    I'm Helen. I'm 12 and I'm in No.1 Middle School. I have three keys, two English books, an eraser and a Chinese dictionary. I have five pencils. But Jill borrows(借) two of them from me. My stuff is in my schoolbag. Susan is my friend. She is 13 and she is in No.3 Middle School. She has three English books, four pens and two dictionaries. They are not in her schoolbag. Where are they? They are everywhere in her room — on the bed, under the desk and on the chair.

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 实验室用硝酸钾固体配制100.0g溶质质量分数为3.0%的硝酸钾溶液，下列说法正确的是（　　）