Statics of immersed objects
objects immersed in a liquid
The weight of a piece of uniform rod is proportional to its length. For example, if a rod (of weight W) has length l metres and x metres are under water, then the weight of the wet part is and its buoyancy is (by rule 3, above).
Divide the object into two parts: the wet and the dry. Treat these as though they are separate. Draw a force diagram, showing the weight, tension, reaction and the buoyancy, acting upward through the centre of buoyancy of the wet part. Now, treat the problem like any statics problem: Forces up = Forces down ; clockwise moments = Anti-clockwise moments.
SF Notes to follow