This document discusses buoyant force and Archimedes' principle through examples and a problem solving activity. It defines buoyant force as the upward force exerted by a fluid on a submerged object. Archimedes' principle states that the buoyant force is equal to the weight of the fluid displaced by the object. The document presents an activity to calculate buoyant forces on clay balls and basins submerged in water to illustrate these concepts.