据水面3.5米,则所受到的压强 p = ρ g h = 1.0*10^3* 10* 3.5 = 3.5*10^4pa
洞的面积为0.0003m^2
所以根据 F = ps = 3.5*10^4 * 0.0003 = 10.5N
搞定