From Mechanics

We start by converting the speed to SI units.

\displaystyle 60\text{ km/h }=\frac{60\times 1000}{60\times 60}=\frac{50}{3}=\text{16}\textrm{.}\text{7 m}{{\text{s}}^{\text{-1}}}

The diagram shows the forces on the car.

\displaystyle F=m\frac{{{v}^{2}}}{r}=1000\times \frac{{{\left( \frac{50}{3} \right)}^{2}}}{50}=5556\text{ N}

\displaystyle R=mg=9800

\displaystyle \begin{align} & F\le \mu R \\ & 5556\le \mu \times 9800 \\ & \\ & \mu \ge \frac{5556}{9800} \\ & \mu \ge 0\textrm{.}567 \\ \end{align}