Drag Force Experienced by a Body Moving through a Rarefied Gas

Understanding how the drag force acts on a body is important in many areas of science and technology, and substantial efforts have been made to evaluate this force with high precision, particularly in the realm of fluid mechanics. In this paper we introduce a simple model based on kinetic theory that allows us to estimate the drag force on a body moving through a rarefied gas, where the assumptions of fluid mechanics no longer apply. Despite the simplicity of this model, the results agree quite well with the exact solutions. However, the simplicity of the model allows it to be used with undergraduate students in an introductory course.