如图所示，圆柱形容器A和B放在水平地面上，它们的底面积分别为2×10－2米2和1×10－2米2。A容器中盛有0.2米高的水， B容器中盛有0.3米高的酒精。（ρ酒精＝0.8×103千克/米3）求：
①A容器中水对容器底部的压强p水。
②B容器中酒精的质量m酒精。
③若在两容器中抽出相同质量的水和酒精后，剩余液体对容器底部的压强分别为p水'和p酒精'。
请计算当p水'＞p酒精'时，抽出液体的质量范围。
解：①p水＝ρ水gh水 ＝1×103千克/米3×9.8牛/千克×0.2米 ＝1960帕
②m酒精＝ρ酒精V酒精＝0.8×103千克/米3×1×10－2米2×0.3米 ＝2.4千克
③若p水'＞p酒精'
则F水＞F酒精；所以（m水-△m）gS水＞（m酒精-△m）gS酒精
代入数据1000kg/m3×2×10-2m2×0.2m-△m×2×10-2m2＞（2.4kg-△m）×1×10-2m2；
整理可得△m＞0.8kg；
抽出液体的质量范围：0.8kg＜△m＜2.4kg．
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sweep the floor, wash the clothes and dishes in the afternoon. I want to visit my grandfather at 3 o'clock. I'm going to buy a comic book at the bookstore. I'm going to watch TV in the evening. I'm going to go to bed at 10 o'clock at night. ( ) 1. Sarah is in bed at 9 o'clock on Sunday morning. ( ) 2. Sarah and her mother are going to clean the room on Sunday morning. ( ) 3. Sarah wants to visit her aunt in the afternoon. ( ) 4. She is going to buy a magazine at the bookstore. ( ) 5. Sarah is going to watch TV at 10 o'clock at night. ( ) 6. Sarah is helpful at home. ( ) 7. Sarah doesn't like comic books. ( ) 8. Sarah is not going to sweep the floor on Sunday. ( ) 9. Sarah is going to watch TV in the evening. ( ) 10. Sarah is a good girl. |