Until then, you could try performing the falling-ball experiment in a more viscous fluid where the Reynolds number will be low enough to make the result valid. You can divide the dynamic viscosity by the density to get the kinematic viscosity of water. The kinematic viscosity is the dynamic viscosity divided by the. I will try to find someone else who is more knowledgeable than I. The unit centiPoise 0.001 Pa s and is is sometimes written mPa s. I have no experience in measuring viscosity, just what I learned in school. Unfortunately, the equation you are using is for laminar flow.
I calculate that your data indicates a high Reynolds number, and thus indicates that you have turbulent flow around the ball. One other consideration involves the “Reynolds number.” For any fluid-flow situation, this number determines whether the fluid moves as “laminar flow” or “turbulent flow.” See. While these are issues affecting the accuracy of your result, they don't seem big enough to account for the three orders of magnitude error. In water and with so short a falling distance, maybe it's not so small. For more viscous liquids, the ball gets to terminal speed quickly, so the error is small. Made-for-purpose falling-ball viscometers measure the falling time between two points that are below the liquid surface so the ball has time to get up to speed. The formula assumes that you measure the falling velocity after the ball has accelerated to it's final speed. Could you use a longer column of water and a less dense ball to make the fall time longer? Consider a fluid placed between two parallel plates, and the top plate is pushed parallel to the bottom plate with constant. Pa·s is equivalent to N × s ÷ m 2 or kg/m/s. A pascal-second (Pa·s) is a derived metric SI (System International) measurement unit of dynamic viscosity.
I'm not sure why you are getting the wrong answer, but here are a few comments.ġ.2 sec is a very short time to measure by eye and hand. The pascal-second is a unit of measurement of dynamic viscosity.