Force/density difference in liquid question

[lys]

Hello,
I am wondering how one can calculate the upwards force of a less dense object within a denser liquid based on the object's volume (or mass) and density, i.e of an air balloon in water.

I've already searched for an answer for a while, but just don't seem to be asking google the right questions.

 

[Doc Al]

Look up buoyancy and Archimedes's principle. Try: http://hyperphysics.phy-astr.gsu.edu/Hbase/pbuoy.html"

 

[HallsofIvy]

Start with Archimedes's principle: an object submerged in water (or other liquid or gas) displaces its own volume. The upward force (bouyant force is, I think, the technical term) is just the weight of the fluid displaced minus the weight of the object. Since weight= mg, that would be g(mass_fluid- mass_object). Since, further, mass is just density time volume, the force is gV(density_fluid- density_object), where V is the volume of the object.