Answer
$0.87$
Work Step by Step
As we know that
$N=Tsin(\theta)$
and the force of friction is given as
$f=\mu N$
$\implies f=\mu Tsin(\theta)$
Now we can find the torque as
$fR-Tcos(\theta)(\frac{1}{2}R)=0$
This simplifies to:
$\mu sin(\theta)-cos(\theta)(\frac{1}{2})=0$
$\implies \mu=\frac{1}{2tan(\theta)}=\frac{1}{2tan(30)}=0.87$
