The Archimedes principle is one the of basic laws in physics. This law explains why some objects can swim and why other objects sink. The Archimedes principle takes effect in any fluid; liquids and gases or mixture of them both are all considered fluids. In brief, the Archimedes principle can be expressed in following way. If one object is inside fluid then this object is under influence of a buoyancy force which is proportional to the weight of the fluid which was displaced by this object. The buoyancy force has got the opposite direction to the gravity force. The **buoyancy** force is given by a formula:

**F**_{B}=-ρ_{fluid}·V_{fluid}·**g**

Value of buoyancy force is given by formula:

F_{B}=ρ_{fluid}·V_{fluid}·g

An iceberg swims in sea. The iceberg's tip is staying afloat what means that it is above the water level. The subject of example is to calculate volume of the icberg's tip that is submerged in the water. This exercise will give an answer that will be relation between volume of the iceberg's tip and the volume of rest of iceberg that is submerged in the water and simply invisible for ships and boats.

An orb has a small sphere hollowed inside. The bigger orb has the radius R. The smaller sphere, which is hollowed inside the bigger sphere, has the radius r. The small orb's density is zero because it is a vacuum. The bigger orb has density ρ'. The difference between both radiuses is d=R-r. The subject of example is to find a distance d which will allow the ball to float and be in half under the water level i.e. the ball has to submerged in half.

A roller is sinking in water. A subject of example is to find the roller's diameter. The forces which work on the roller while it is sinking are known and their values are the inputs to the example.