(1)物体受到的浮力为F浮=G-F=5N-3N=2N;(2)∵F浮=ρ水gV排,∴物体的体积为V=V排= F浮 ρ水g = 2N 1.0×103kg/m3×10N/kg =2×10-4m3=200cm3;(3)∵G=mg,∴物体的质量为m= G g = 5N 10N/kg =0.5kg,∵ρ= m V ,∴物体的密度为ρ= m V = 0.5kg 2×10?4m3 =2.5×103kg/m3.故答案为:2;200;2.5×103.