Hi thanks for your reply! Yes I'm defining that to be theta. Could you please elaborate on this? It's still not clear to me why I can't define N that way.
The first part is easy, we have 2T= Mg
T= 0.5 Mg
Now for the second part where I'm having trouble understanding Morin's solution:
I take the normal force on a small circle arc to be N, we know that the y component of the normal force must be balance with Mg for the whole disk, therefore
Ny =...