Fuel used up in a vehicle depends on the total distance travelled, not displacement. Displacement is the shortest distance between the initial and final positions, which can be zero even when a vehicle has travelled a long path. For instance, if a vehicle starts at point O, travels to point A, and returns to O, the displacement is zero, but the vehicle still consumes fuel for the entire journey. The fuel consumed corresponds to the actual path length covered, which is the total distance travelled. Since displacement does not account for the actual path taken, it cannot determine fuel consumption.