Physics and Astronomy Labs/Archimedes' principle
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Archimede's Principle Lab
Archimedes' principle indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces and it acts in the upward direction at the center of mass of the displaced fluid.
The downward force on the object is simply its weight. The upward, or buoyant force on the object is that stated by Archimedes' principle, above. Thus the net upward force on the object is the difference between the buoyant force and its weight. If this net force is positive, the object rises; if negative, the object sinks; and if zero, the object is neutrally buoyant - that is, it remains in place without either rising or sinking.
For a fully submerged object, Archimedes' principle can be reformulated as follows:
apparent immersed weight = weight of object - weight of displaced
The density of the immersed object relative to the density of the fluid can easily be calculated without measuring any volumes:
density of object / density of fluid = weight / (weight- apparent immersed weight)