Physics Question?

Question

A 30kg block is at rest on a 31 degree incline. The coefficients of static and kinetic friction are .65 and .55 respectively. The accleration of gravity is 9.8m/s2. What is the frictional force acting on the 30 kg mass. Also, what is the largest angle which the incline can have so the mass does not slide down the incline

Answer 1

1, Normal to the surface force
N= W cos(31)
N=mg cos(31)

f= uN
f=.65 x 30 x 9.8 x cos(31)

2. Max angle A?

f=F=uWcos(A)
f= W sin(A)=uWcos(A)
tan(A)=u
A= arcTan(u)
A=arcTan(.65)=
A=33 degrees