 Solution

On this circle the radial coordinate is constant, $r=2$, so $\dot{r}=\ddot{r}=0$. The velocity is a tangent vector to the circle in the anticlockwise direction, represented by $i{e}^{i\theta }$ when $\dot{\theta }>0$. Substituting into part (b),The inward component is the centripetal acceleration; the transverse component allows the speed to change. Anticlockwise motion does not imply uniform speed or $\ddot{\theta }=0$. The preceding figure includes the required tangent arrow.