Dynamics question regarding moment of inertia

[chicagobears34]

Hi, I have a question regarding a dynamics question that be found here:http://by.genie.uottawa.ca/~mess/files/MCG_2107/MCG2107_M2005_p2.pdf, It is the first problem on that link (labeled number 2.)

I did ƩFx, ƩFy, ƩM_G which allowed me to find angular acceleration, frictional force, and acceleration of G.
Friction force and acceleration of G were correct but angular acceleration was wrong.
My equations were:
ƩFx: -μ_kN + T cos(30)=ma_G
ƩFy: N-mg+Tsin(30)=0
ƩM_G: Tcos(30)(0.075)-μ_kN(0.2)=Iα
ΔFf=17.6N, Ag=1.0281, α=8.84
α should be equal to .295

 

[tiny-tim]

hi chicagobears34!

ƩM_G: Tcos(30)(0.075)-μ_kN(0.2)=Iα

why cos(30) ?