为了加深学生对浮力产生的认识,可用三块大小相同的方木块(边长3-4厘米为宜,过小不利于观察,过大没有合适的玻璃水槽),分别编号为A、B、C。在每个木块上任选一面作底面,分别照图所示涂微量(不能多)凡士林,A涂中间,B涂三边和第四边的一半,C四边都涂,向学生说明涂在A块的凡士林比C块的多,面积也大。然 In order to deepen students' understanding of buoyancy, three square blocks of the same size (side length 3-4 cm is suitable, too small for observation, too large no suitable glass sink) are respectively numbered as A, B, C. In each block on either side of the bottom, respectively, coated with trace amounts (not more) Vaseline, A coated middle, B coated side and the fourth side of the half, C sides are painted, to the students painted A block of Vaseline more than C, the area is also large. Of course