Why do these two Stokes law formulas give different results?

LaurenG · Feb 1, 2009

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 -

$Equation: Vt = g d^2 (ρp − ρm) / (18 μ), with the numerator and denominator written as a fraction.$

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

Any idea why they are different ?
Thanks.

davieddy · Feb 1, 2009

LaurenG · Feb 2, 2009

davieddy said:

d=2R

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

Why do these two Stokes law formulas give different results?

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