Investigating Stokes Law: Different Formulas, Different Results?

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SUMMARY

This discussion centers on Stokes' Law and the discrepancies between two formulas used to calculate the settling velocity of particles. The first formula, Vt = gd²(Pp - Pm) / 18u, and the second formula, V = 2/9 * d² * g * (Pp - Pm) / u, yield different results due to variations in constants and assumptions regarding fluid dynamics. Understanding these differences is crucial for accurate calculations in fluid mechanics and particle settling analysis.

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LaurenG
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Hello all.

I'm investigating a little bit about stokes law in order to understand the settling velocity of falling particles and on the net i encountered with 2 different formulas and i simply can't find the reason why they are different. every formula gives me a different answer.
The 2 formulas are :
1. Vt=gd^2(Pp-Pm)/18u -
stokes_law_terminal_velocity.png

2. V=2/9*d^2*g*(Pp-Pm)/u -
3dbef61d20c1951c09a727ff8d4a809c.png


Any idea why they are different ?
Thanks.
 
Last edited:
Physics news on Phys.org
d=2R
 
davieddy said:
d=2R

Silly me, i knew it's something stupid.
Thanks :)
 

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