Experiment 4 - Drag coefficient

Any solid object moving through a viscous fluid will experience a resistance or 'drag force'. This is one of the most important aspects of fluid mechanics and it must be remembered that common fluids like air and water must be considered viscous in this context. An understanding of fluid drag forces is therefore essential to the proper design of aircraft, trains, automobiles, ships, submarines, tall structures, jetties and off-shore structures of all kinds. It is equally relevant to the mechanics of particles falling under gravity; raindrops and parachutes in air, sand grain in air or water and the settlement of kinds of all suspended solid particles in water. The drag force depends on a number of variables and one of the more important is the shape of the moving body. In this experiment, only spherical objects are used. This enables the relationships between more easily described parameters such as velocity, fluid viscosity and body density to be explored experimentally. For spherical objects, the radius is a sufficient description of the object although the specific weight of each material used must be determined as well.