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?
I assume that the angle of inclination is
we know for that
from the FBD diagram we can conclude that
substituting the values you can get your answer (here a in the image is the angle you provided)