A Bernoulli's Law Lab in a Bottle

Bernoulli's law is a fundamental relationship in fluid dynamics that is covered in most introductory physics courses. Basically a statement of conservation of energy for an open fluid system, Bernoulli's law is often used in labs and examples to analyze the lift force on a fixed wing or the forces on objects in a fluid flow.^1–4 Although these are legitimate uses of the law, they do not introduce students to the way in which several concepts, such as Bernoulli's law and the conservation of mass, are used in combination to study the dynamics of fluid systems. Thus, to give students an easily understandable introduction to this method of analysis, we present a laboratory experience in which the drain time of water flowing out of an inverted soda bottle is measured and calculated for a set of easily interchangeable exit holes.