Measuring Drag Force in Newtonian Liquids

Abstract

The experiments described in this paper have two goals. The first goal is to show how students can perform simple but fundamental measurements of objects moving through simple liquids (such as water, oil, or honey). In doing so, students can verify Stokes' law, which governs the motion of spheres through simple liquids, and see how it fails at higher object speeds. Moreover, they can qualitatively study fluid patterns at various object speeds (Reynolds numbers). The second goal is to help students make connections between physics and other sciences. Specifically, the results of these experiments can be used to help students understand the role of fluid motion in determining the shape of an organism, or where it lives. At Saint Josephs University we have developed these experiments as part of a newly developed course in biomechanics where both physics and biology undergraduate students bring their ideas and expertise to enrich a shared learning environment.

Estimating the settling velocity of fine sediment particles at high concentrations

“…The estimation of the terminal fall velocity (settling velocity) of particles within a fluid under gravity is a subject of interest among a wide range of scientific disciplines in physics, chemistry, biology, and engineering. The terminal fall velocity calculation from Stokes' Law is usually taught in introductory courses of physics of fluids as an approximate relation, at low Reynolds numbers, for the drag force exerted on an individual spherical body moving relative to a viscous fluid 2,3 .…”