AROUND 11:30 AM, I WAS DRIVING SOUTH ON A TWO LANE ROAD, AT APPROX. 25 MPH. THE BLACK VEHICLE IN FRONT OF ME APPLIED THE BRAKES AND STOPPED. I WAS ABOUT 4 CAR LENGTHS BEHIND THE BLACK VEHICLE WHEN I QUICKLY APPLIED THE BRAKE PEDAL. THE BRAKE PEDAL WENT TO THE FLOOR AND MY CAR DID NOT STOP NOR EVEN SLOWED DOWN. I PUMPED THE BRAKE PEDAL TWO MORE TIMES, AGAIN, AND THE CAR DID NOT STOP NOR SLOWED DOWN UNTIL I HIT THE BLACK VEHICLE IN FRONT OF ME.