coefficient of kinetic friction problem?

Question

a 44 kg block is pushed along the ceiling with a constant applied force of 85.0 N that acts at an angle of 55.0degrees with the horizontal. The block accelerates to the right at 6.00m/s^2. Determine the coefficient of kinetic friction between the block and the ceiling

Answer 1

Force of friction equal to the product of the coefficient of friction u and normal to the surface force (or the force with which the object is pressed against the ceiling)
f= uN
f=u(Fsin(55) - mg))

The total force acting on the block is the difference between the applied force in the horizontal direction Fh and force of friction f.
Ft=Fh-f
Ft=Fcos (55) - u(Fsin(55) - mg))
Also Ft=ma

we have

u=[Fcos(55) - ma]/(Fsin(55) - mg))