Task: Question Answering
Input (English): Context: Ugh . Finally , with him pushing and me steering , we got it out . Then I backed it down and got to fly up the hill ( which is the only way to do it w / out 4 wheel drive ) . That was kinda fun . 
Question: Why does backing up then speeding out a hill help one without four wheel drive ?
Output (English): The car is able to build up momentum to scale a hill or mud or some surface which is slowing the car down.