How can we determine viscosity from a graph using Poiseuille's equation?

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SUMMARY

To determine viscosity using Poiseuille's equation, one must plot the height of a water tank against the rate of flow. The gradient of this graph does not directly provide viscosity; instead, it is necessary to rearrange the equation to isolate viscosity (η). The correct formula derived from the equation is η = (πρr^4)/(8l * gradient), where ρ is the fluid density, r is the radius of the pipe, and l is the length of the pipe. This approach allows for the calculation of viscosity based on the slope of the plotted graph.

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if we use Poiseuille's equation, plotting the varying height of a water tank againts the rate of flow, does the gradient of the graph tell us the viscosity, or do we re-arrange the equation to find viscoisty.

Thanks
 
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jsmith613 said:
if we use Poiseuille's equation, plotting the varying height of a water tank againts the rate of flow, does the gradient of the graph tell us the viscosity, or do we re-arrange the equation to find viscoisty.

Thanks

Gradient = (πρr^4)/8ηl

Re-arranging this gives: η= (πρr^4)/(8l ∗gradient)
BUT if y = mx + c
y = η
and x = (πρr^4)

So how do we use Poiseullie's equation to find viscosity, when we plot height of tank against (x axis) rate of flow (y)

thanks
 

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