Answer
Please see the work below.
Work Step by Step
We know that the centripetal force should be equal to the force of gravity that is
$mg=\frac{mv^2}{r}$
This simplifies to:
$v=\sqrt{rg}$
We plug in the known values to obtain:
$v=\sqrt{(0.85)(9.8)}=2.9\frac{m}{s}$
