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1 教师演示实验,复习旧知,引入新课 出示实验器材:量筒、弹簧秤、金属块、装有水的烧杯。向学生提出三个问题:(1)用这些器材怎样测量金属块浸在水中受到的浮力?(2)怎样知道金属块浸入水的体积(即金属块排开水的体积)?(3)怎样计算金属块排开水的重力?边启发学生正确回答这些问题;边演示实验,同时要求学生注意,测浮力时金属块不能与容器底、壁接触。然后,将称量法求浮力的公式F_浮=G-G′(G为金属块在空气中的重力,G′为金属块在水中的视重);金属块排开水的体积公式:V_排=V_2-V_1(V_1是未浸金属块时量筒中水的体积,V_2是浸入金属块时水面到达的刻度);金属块排开水的重力的计算公式:G_(排液)=ρ_液gV_排写在黑板上。接着请学生根据自己的生活经验谈谈物体受到浮力的大小跟哪些因素有关。学生的
1 The teacher demonstrates the experiment, reviews the old knowledge, and introduces new courses to show the experimental equipment: measuring cylinders, spring scales, metal blocks, and beakers filled with water. Ask students three questions: (1) How do you measure the buoyancy of a metal block immersed in water using these devices? (2) How do you know the volume of metal immersed in water (ie, the volume of water in a row of metal blocks)? (3) How to calculate The gravity of the row of boiling water in the metal block inspires students to answer these questions correctly. While demonstrating the experiment, students are also required to pay attention to the fact that when the buoyancy is measured, the metal block cannot contact the bottom or wall of the container. Then, the buoyancy formula F_float=GG′ (G is the gravity of the metal block in the air, G′ is the apparent weight of the metal block in the water) is calculated by the weighing method; the volume formula of the metal block row is: V_ = V_2-V_1 (V_1 is the volume of water in the graduated cylinder when the metal block is not immersed, V_2 is the scale that the surface of the water reaches when immersed in the metal block); the calculation formula of the gravity of the molten metal in the row of the metal block: G_ (discharge) = ρ_liquid gV _ Queue written on the blackboard. Then ask students to talk about the factors related to the size of the buoyancy of the object according to their own life experience. student’s