Nails are made up of iron not of phosphorus and barium.
As both phosphorous and barium are relatively weaker than iron ,phosphorus breaks easily and barium is also fairly weak. Iron nails are already also not that strong, but their weight and strength are sufficient.
So the nails are made up of iron.
Volume= Mass/ Density= 20/184
= 0.108 cubic cm
30 kg m/s
momentum = mass x velocity = 10 x 3 m/s =30 kg m/s
