Archimedean Principle

Archimedes was the first man who discovered the relation between the displaced water and the buoyancy. The Archimedean theorem named after him indicates:

The buoyancy of a body in a liquid substance equals the weight of the liquid substance which has been displaced by the body.

To simplify the reflection often the mass instead of the weight force is considered because the mass is proportional to the weight force (G=m∙g).

Exapmles:
A body which displaces 80 g water while beeing dipped into water, seemingly weighs 80 g less than before.
A body which displaces 150 g water while beeing dipped into water, seemingly weighs 150 g less than before.