The acceleration vector shall change the component of velocity u_II along the acceleration vector.

$r=\frac{v^2}{a_{\text{n}}}$

The radius of curvature $r_{\min }$means v is minimum and a_n is maximum. This is at the point $\mathrm{P}$ when the component of velocity parallel to the acceleration vector becomes zero, that is u_II = 0.



$\therefore R=\frac{u_{\perp }^2}{a}=\frac{4^2}{2}=8\text{ m}$