At the bottom of a loop in the vertical ( $r-\theta$ ) plane at an altitude of $400 \mathrm{m}$, the airplane $P$ has a horizontal velocity of $600 \mathrm{km} / \mathrm{h}$ and no horizontal acceleration. The radius of curvature of the loop is $1200 \mathrm{m}$ For the radar tracking at $O,$ determine the recorded values of $\ddot{r}$ and $\ddot{\theta}$ for this instant.