1、P=pgh=1x10^3x10x20=2x10^5Pa2、F=mg=0.5x10^3x10=5x10^3N3、铁牛体积V=m/p=15.8/7.9=2m^3F=pgV=1x10^3x10x2=2x10^4NF 浮筒=pgV=1x10^3x10x40=4x10^5NF浮=F+F浮=4.2x10^5NF=mg=(15.8+0.5)x10^4=1.63x10^5NF富裕=(4.2-1.63)x10^3=2.67x10^5N=26.7t40-26.7=13.3t至少排水13.3t