Final answer:
When a vehicle is facing downhill and is backing up the hill, it has a disadvantage because it needs to overcome the force of gravity pulling it down.
Step-by-step explanation:
When a vehicle is facing downhill and is backing up the hill, it is important to consider the forces acting on the vehicle. In this situation, the force of gravity is working against the vehicle's motion. So, the vehicle facing downhill has a disadvantage when backing up the hill because it needs to overcome the force of gravity pulling it down.
For example, if a truck is parked at the top of a hill and the truck driver lets it run freely down the hill, the truck will gain momentum due to the force of gravity. However, when the driver wants to back up the hill from a stationary position, the truck will need to overcome the force of gravity to move in the opposite direction.
This concept is similar to a car coasting down a hill and coming to a stop at the bottom due to friction and other resistive forces. When the car tries to go back up the hill, it needs to exert more effort to counteract the forces working against it and move in the opposite direction.