# An object with a mass of 8 kg is on a plane with an incline of  - pi/12 . If it takes 12 N to start pushing the object down the plane and 9 N to keep pushing it, what are the coefficients of static and kinetic friction?

May 14, 2017

I assume that the angle of inclination is $\frac{\pi}{12}$ instead provided ,
we know for that

from the FBD diagram we can conclude that

${f}_{\text{static}} = m g \mu \cos \theta$

${f}_{\text{dynamic}} = m g \mu \sin \theta$

substituting the values you can get your answer (here a in the image is the angle you provided)

${\mu}_{\text{static")=f_("static}} / \left(m g \cos \theta\right)$

${\mu}_{\text{dynamic")=f_("dynamic}} / \left(m g \sin \theta\right)$