The $30-\mathrm{kg}$ gear $A$ has a radius of gyration about its center of mass $O$ of $k_{o}=125 \mathrm{~mm}$. If the $20-\mathrm{kg}$ gear rack $B$ is subjected to a force of $P=200 \mathrm{~N}$, determine the time required for the gear to obtain an angular velocity of $20 \mathrm{rad} / \mathrm{s}$, starting from rest. The contact surface between the gear rack and the horizontal plane is smooth.