I WAS DRIVING AT ABOUT 25MPH ON MONTGOMERY DRIVE IN PHILADELPHIA (CITY STREET) IN THE MORNING OF 12/9/2019. IT WAS RAINING LIGHTLY. THE CAR IN FRONT OF ME WAS ABOUT 4 TO 5 CAR-LENGTHS AHEAD. IT BRAKED AS ANOTHER CAR TRIED TO CUT IN, AND I ALSO IMMEDIATELY BRAKED. MY BRAKE FELT GRINDING AND MY CAR CONTINUED TO SLIDE INTO THE BACK OF THE CAR IN FRONT OF ME.