h2. Why Drag Analysis is necessary

h3. Velocity Gradients

The velocity gradients found in each tube over the range of critical velocities can be found in Table 1. By comparing the velocity gradients in table 1 and the results table from the [flow rate experiment|PSS flow rate experiment] it can be determined that once the velocity gradient in the tube reaches a certain value, failure occurs. From the data it appears that failure occurs around 2.4 1/s, as velocity gradients beyond this value correspond with failure in the two smallest tubes sizes tested. 

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{excel:file=PSS flow rate experiment^DataAnalysis_aguaclara.xls |sheet=Velocity Gradient Table}
*Table 1. Results: The Velocity Gradients for the Tested Critical Velocities*
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h3. Force balance on the floc