Forces in Fluids: Drag and Buoyancy [IB Physics SL/HL]

This video explores fluid dynamics, beginning with buoyancy force and its relationship to density, explaining how to determine if an object will sink or float. It defines density as mass to volume ratio, noting its constancy for solids and liquids versus variability for gases. The discussion then covers Archimedes' Principle, stating that buoyancy equals the weight of displaced fluid, and mathematically demonstrates how comparing object and fluid densities predicts sinking or floating. For floating objects, the video explains how the submerged volume balances gravity, deriving a ratio of densities to submerged height. Finally, it addresses drag forces in fluids, detailing how air resistance affects an object's kinematics, leading to decreasing acceleration and eventually a constant terminal velocity. Stokes' Law is introduced to quantify drag force on spherical objects, highlighting the role of fluid viscosity, which is defined as resistance to flow and its inverse relationship with temperature.