题目

 “My kids really understand solar and earth-heat energy,” says a second-grade teacher in Saugus, California. “Some of them are building solar collectors for their energy course.” These young scientists are part of City Building Educational Program (CBEP), a particular program for kindergarten through twelfth grade that uses the stages of city planning to teach basic reading, writing and math skills, and more. The children don’t just plan any city. They map and analyze the housing, energy, and transportation requirements of their own district and predict its needs in 100 years. With (北京市西城区)如图(甲)所示,金属块A在木块B上,木块恰好浸没在水中.将金属块放入水中,容器底对金属块的支持力是2牛;木块静止时,有2/5的体积露出水面,如图(乙)所示.已知木块的体积是金属块体积的5倍,求:金属的密度和木块的重力.(g=10牛/千克)??(甲)???????(乙)
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