A)incompatible because irreconcilable me something that can not be compatible
A thimble is the correct answer
The net force on the bookcase in the direction of its motion is
∑ F = 65 N - F[friction] = (41 kg) (0.12 m/s²)
so that friction has a magnitude of
F[friction] = 65 N - (41 kg) (0.12 m/s²) = 60.08 N
The net force on the bookcase perpendicular to the surface is
∑ F = F[normal] - (41 kg) g = 0
so that
F[normal] = (41 kg) g = 401.8 N
If µ is the coefficient of kinetic friction, then
F[friction] = µ F[normal]
so that
µ = F[friction] / F[normal] = (60.08 N) / (401.8 N) ≈ 0.15
