A 32 kg box sitting on a ramp has a coefficent of 0.21. If the ramp is raised, at what angle will the box begin slipping?

Answer 1

coefficent of friction?

force downward=Fn*mu=mgCosTheta*mu
force down the ramp= mg*sinTheta

set these two forces equal
mgCosTheta*mu=mgSinTheta
I think you get

tan Theta=mu
check that.