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I am investigating about viscosity of fluids and I found the following equation to calculate the viscosity: $$\nu = \frac{2(\rho_s-\rho_l)\cdot g \cdot r^{2}}{9\cdot\Delta v} $$

The experiment consists of having a tube with whatever liquid you would like to measure and drop a ball and see at which speed it reaches the bottom.

$\rho_s$ is the density of the sphere, $\rho_l$ the density of the liquid, $g$ the acceleration of gravity, $v$ the final velocity and $r$ is the radius of the ball.

The problem is, I really do not know where this equation comes from nor do I know if it is correct.

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  • $\begingroup$ Sounds like a job for Stokes' law. $\endgroup$ – Qmechanic Dec 27 '18 at 13:19
  • $\begingroup$ This comes from applying Stokes law and Archemides principal to determine the terminal velocity of a sphere falling through a fluid. $\endgroup$ – Chet Miller Dec 27 '18 at 14:36

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