an object of mass 4 kg is placed on an inclined plane at an angle of 60. if the object slides down the plane with an acceleration of 3m/s, what is the coefficient of the kinetic friction

The forces on the y axis are:

N-mgcos (60) = 0, wich becomes

N=mgcos (60)

Rember that the friction force is always contrary to the motion of an object and its formula is f=μ * N

The forces in the x axis are:

-f + mgsin (60) = m * a

-μ*mgcos (60) + mgsin (60) = m*a,

μ = (m*a - mgf=μ[sin (60)) / (mgcos (90))