Answer
$PQ = \frac{\sqrt{3}}{2}$
Work Step by Step
Let $y = PQ$:
$\frac{y}{r} = sin ~60^{\circ}$
$\frac{y}{r} = \frac{\sqrt{3}}{2}$
$y = (r)~(\frac{\sqrt{3}}{2})$
$y = (1)~(\frac{\sqrt{3}}{2})$
$y = \frac{\sqrt{3}}{2}$
$PQ = \frac{\sqrt{3}}{2}$