The net acceleration of the car is the vector sum of centripetal acceleration and tangential acceleration. By Newton’s second law the net force of friction acting on the car is equal to mass multiplied by net acceleration.
Here, at any time t, the speed of the car becomes V,
the net acceleration in the plane road is \(\sqrt{\left(\frac {v^2}R\right)^2 + a^2}\).
This acceleration is provided by the frictional force. At the moment car will slide