Answer
a) $d=0.334m$
b) $F=1.01KN$
Work Step by Step
(a) We know that
$d=2r$
$d=2\frac{a_{cp}}{\omega^2}$
We plug in the known values to obtain:
$d=2\frac{6840(9.81)}{6050(\frac{1min}{60s}(\frac{2\pi}{rev}))^2}=0.334m$
(b) We can find the force as below
$F=ma_{cp}$
We plug in the known values to obtain:
$F=0.0150(6840)(9.81)$
$F=1.01\times 10^3=1.01KN$