Ask Me Help Desk - Rearranging stokes law

Quote:

Originally Posted by cathwan

Please can someone help me rearrange this equation so the U is the subject?

v= (pp-pf)/u x 2/9 x g x r^3

THANKYOUUU

Starting with
$ v = \frac 2 9 \frac {(\rho_p- \rho_f)}{\mu} g r^2 $
(note that I changed the formula a bit to agree with Stokes' Law) simply multiply both sides by $\mu$ and divide both sides by $v$ :

$ v \times \frac {\mu} v = \frac 2 9 \frac {(\rho_p - \rho_f)}{\mu} g r^2 \times \frac \mu v \\ \cancel v \times \frac {\mu} {\cancel v }= \frac 2 9 \frac {(\rho_p - \rho_f)}{\cancel \mu} g r^2 \times \frac {\cancel \mu} v \\ \mu= \frac 2 9 \frac {(\rho_p - \rho_f)}{v} g r^2 $