Rotational energy problem

__Question:__

http://i.imgur.com/qWrXh.jpg

__(Correct) Answers:__

(a) 0.146938776m

(b) 0.102857143m

__My work:__

First off, my problem likely lies with the fact that it is rotating instead of being translated like in regular translations (like a ball being thrown etc). I remember my teacher saying something of the sort and I checked my notes and it seems to be about moment of inertia which has me lost. I have a feeling that in the following my mistake lies with the initial kinetic energy.

Ok so what I did for (a) which gives me half the right answer is:

Ui = 0, Ki = 1/2 * m * v^2, Kf = 0, Uf = mgh

Ef = Ei

mgh = 1/2 * m * v^2

gh = 1/2 * v^2

h = (1/2 * v^2)/g

h = 1/2 * 1.2^2 / 9.8

h = 0.073469388

as for (b), it seems to be very similar.

Any help would be GREATLY appreciated!

Thanks in advance!