A driver drives at 50 km / h, but suddenly has to apply the emergency brake. The acceleration during braking is a = 0.50g, where g is the acceleration of gravity. How long will be the braking distance? How many times longer will the braking distance be if the car drives twice as fast?

b) Show that the coefficient of friction must be at least = 0.50 for the car to able to slow down as in the previous sub-task. Assume that the road is straight and horizontally everywhere, and disregard the air resistance.