Measure that weight g of an object with a spring dynamometer, immersing the object in wat, and reading the pointer f' of the dynamometer, wherein the buoyancy of the object is f = g-f'; The content of Archimedes principle is that an object immersed in a liquid is subjected to upward buoyancy, which is equal to the gravity of the liquid it displaces, that is, F float =G row = ρ liquid? g？ V. Drainage;
If it is a floating or suspended object, the buoyancy is equal to gravity, so it is enough to measure the weight of the object directly.
So the answer is: f = g-f'; F float =G row = ρ liquid? g？ V. Drainage; F=G。