The expression for the centripetal force in a uniform circular motion is:
[tex]F=m \frac{v^2}{r} [/tex]
where m is the mass, v the speed and r the radius of the circle.
The car in our problem has a mass m=1500 kg and a speed v=18 m/s. The intensity of the force is F=3313.6 N, so we can re-arrange the formula to find r, the radius of the circle:
[tex]r=m \frac{v^2}{F}=(1500 kg) \frac{(18 m/s)^2}{3313.6 N}=146.7 m [/tex]
