physics problem too difficult?

[Eric J]

Hi, I can't seem to get this last part of this problem:
A 13 kg uniform disk of radius R = 0.27 m has a string wrapped around it, and a m = 4.9 kg weight is hanging on the string. The system of the weight and disk are initially at rest. When the 4.9 kg weight is released, it moves down and the disk rotates. Consider the point when the 4.9 kg weight is moving with a speed of 2.1 m/s.

I found that the total K.E.= 25.1 J and that they height of which it has fallen = 0.523 m but I can't figure out the angular acceleration of the disk.

Angular acceleration of disk= ________rad/s^2
I know you're supposed to use this equation: v^2(f)= v^2(i)+2ax
Any help would be greatly appreciated!

No, the following answer are not correct: 27.36 rad/s^2.
THANK YOU OBDU83
I HAVE POSTED THIS QUESTION SEVERAL TIMES AND YOU ARE THE ONLY ONE TO HAVE FIGURED OUT THE CORRECT ANSWER. THANKS SO MUCH.