The angular speed $\left(\omega \right)$ of the child can be calculated as follows:

$\begin{array}{rcl}\omega & =& \frac{2\pi }{3.14}\\ & =& 2 \mathrm{rad} {\mathrm{s}}^{-1}\end{array}$

The formula to calculate the centrifugal force on the child is given by

$F_r=m{\omega }^{2}r ...\left(1\right)$

Substitute the values of the known parameters into equation (1) to calculate the required centrifugal force.

$\begin{array}{rcl}{F}_r& =& 5 \mathrm{kg}\times {\left(2 \mathrm{rad} {\mathrm{s}}^{-1}\right)}^2\times 2 \mathrm{m}\\ & =& 40 \mathrm{N}\end{array}$