化学与物理、生物学科知识交叉渗透的综合题在中考中经常出现，下面举例进行分析．例题如图１所示，等臂杠杆A、B两端各挂一体积相同、质量相等的空心铜球和铁球，在水平位置平衡．现将铜球、铁球分别同时浸没在盛有CuSO４溶液的烧杯中，将发现（球体积变化忽略不计）：ρA．杠 The comprehensive problems of cross-infiltration between chemistry, physics and biology are often present in the examination. The following examples are used for analysis. The example is shown in Fig. 1. The ends of the equal-arm levers A and B each have a hollow copper ball and an iron ball of the same volume and the same mass, and are balanced at the horizontal position. The copper ball and the iron ball are immersed in the beaker containing the CuSO4 solution at the same time and will be found (the change of the ball volume is ignored): ρA. Bar