题干

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2×1022和1×1022。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
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和p酒精。请计算当p>p酒精时,抽出液体的质量范围。

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解:①p=ρgh=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3×1×1022×0.3米=2.4千克③若p>p酒精

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    A day in the life of 18-year-old David Lanster is full if typical teenage stuff: school, baseball practice and homework. And then he starts cooking. “Some nights I'm up until 1:00 a.m. making pies, or even later if we're cooking beef,” said the student at Ransom Everglades High School in Florida, US.

    For the past year, Lanster and Kelly Moran, his classmate, have been hosting fancy dinner parties at Lanster's parents' home. Their meals have 17 courses and are all made by them. Their guests used to give them gifts to thank them until the pair decided to do something nice for charity(慈善). “We got some really great Miami Heat tickets, a nice watch, and many kitchen gadgets(小器具),” Lanster said. “But we wanted to make this something positive for people other than us.”

    Lanster and Moran focused on Common Threads, a charity that aims to teach kids in poor communities to cook and make healthy eating choices. The young cooks ask their guests to give however much they want as payment for their meals. It all goes to Common Threads because Lanster's parents cover their food costs. After their last 12-person event, Lanster and Moran gave $1,600 to the charity.

    Now, they're taking their show out of the kitchen and on the road. They have started to organize private dinner parties with a similar model: the host pays for the ingredients, and the guests make a donation to a charity of their choice.

    Without formal training, Lanster said he had been interested in cooking since he helped his mom in the kitchen when he was very young. He learned how to cook by reading cookbooks and watching TV programs. Outside the kitchen, the two are busy preparing their college applications. Neither of them is sure what they will do in the future, but they're promised their parents that they will leave professional cooking alone until they finish school.