A Simple Apparatus for Demonstrating Fluid Forces and Newton's Third Law

Over 2200 years ago, in order to determine the purity of a golden crown of the king of Syracuse, Archimedes submerged the crown in water and determined its volume by measuring the volume of the displaced water.1 This simple experiment became the foundation of what eventually became known as Archimedes' principle: An object fully or partially immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object. The principle is used to explain all questions regarding buoyancy, and the method is still prescribed for determination of the volume of irregularly shaped objects.2