v=40cm^3=4x10^-5 m^3 , m=50g=5x10^-2 Kg
ρ物=m/v
ρ物=5x10^-2/(4x10^-5)
ρ物=1.25x10^3 Kg/m^3
∵ρ液=1.3x10^3Kg/m^3
ρ液＞ρ物
∴物体漂浮
F浮=G物
F浮=mg
F浮=5x10^-2x10
F浮=0.5N
答：静止时受到浮力是0,5N