Find the acceleration of the disk and the force of friction

[renee1234]

Homework Statement

In the figure, a string is used to pull a disk of radius 18 cm and mass 9.3 kg. If the incline is 37° and the tension in the string is 20 Newtons find the acceleration of the disk and the force of friction on it.

Homework Equations

T=I(alpha)

The Attempt at a Solution

T=I(alpha) --> Rmg=(1/2mR^2+mR^2)(alpha)
I moved the pivot to the contact point of the ramp.
Alpha= 2/3 g/r
a=2/3g
this can't be right though because I didn't figure the tension into it.
I'm lost. please help

[PLAIN]http://www.usi.edu/science/physics/pickett/205/16p3f1.jpg

 

[venkatg]

Draw the free body diagram of the disk. Resolve the components of forces along the incline (x axis) and normal to the incline (y axis). Consider equilibrium of forces along x and y
and moments about the center of disk.

The unknowns are alpha (angular acceleration), F(frictional force) , N (normal force)
and you have 3 equations.

The mass moment of inertia of disk I is = m * r^2/2