Question

3. If the coefficient of friction between tires and roadway is 0.40, what is the minimum radius at which a car can turn on a horizontal road when its speed is 43.75 ft/s?

Answer 1

The force of friction defines the centripetal acceleration the car can withstand:

$$\mu mg=ma_c,\\\space\\ \mu mg=m\frac{v^2}{R},\\\space\\ R=\frac{v^2}{\mu g}=149\text{ ft}.$$