Density and Buoyancy. Density and Buoyancy. Buoyancy is the tendency to rise or float in water or air. The upward force exerted on objects submerged in fluids is called buoyant force .
The Hibernia oil rig has a mass of over 14 000 tonnes, but it floats on the water.
A straight pin has a mass of less than 1 g. However, the pin sinks when placed in water.