因为P=F/S=mg/s=ρVg/s==ρgh
由P=ρgh得h1=P1/ρg=0.04m
h2=0.1m h3=0.25m
V=0.04*0.1*0.25=0.001
F=G=mg=ρVg=2000*0.001*10=20N