Given that,
Volume of body V=10−4m3
Density of iron, ρi=7800kgm−3
Density of water ρw=1000kgm−3
Weight in air,Wa=ρiVg=7800×10−4×10=7.8N
We know that,
Weight in water = weight in air – buoyancy force
Ww=Wa−ρwVg
Ww=7.8−1000×10−4×10
Ww=6.8N
Hence, the weight of body in water is 6.8 N