How does kinetic energy affect the stopping distance of a vehicle traveling at 30 mph compared to the same vehicle traveling at 60 mph?

The vehicle traveling 60 mph is going 4 times as fast. the brakes must do an amount of work that's equal to the original kinetic energy. the brakes exert the same amount of force no matter what the case is, so the stopping distance will be four times as long for the car going 60 mph compared to the car going 30 mph.