1.
侵入水中的体积是 5×10^-4m^2 * 0.1m = 5×10^-5m^3
所以所收的浮力 F=ρgV
因为竖直方向只受浮力和重力,所以(M+m)g = ρgV
(M+m) = ρV = 1000kg/m^3 * 5×10^-5m^3 = 0.05kg
所以玻璃管和细纱的总重是0.05kg
2.(M+m)g = ρ盐水gV'=ρ水gV
所以 ρ盐水 = ρ水 * V/V'= ρ水 * (sh)/(sh') = ρ水 * h/h' = 1000kg/m^3 * (0.1m)/(0.1m-0.01m) = 1.11×10^3kg/m^3