A 4.00 kg block is pushed along the ceiling with a constant applied force of 85.0 N that acts at an angle of 55.0° with the horizontal, as in the figure below. The block accelerates to the right at 6.00 m/s2. Determine the coefficient of kinetic friction between block and ceiling.

Answer 1

y direction:
85sin55 = mg + Fn (note normal is DOWN in this case) Find Fn
x direction:
85cos55-Ff = ma Find Ff
mu = Ff/Fn