ELI5: Why do cars, even when fully stopped on a flat (or slightly inclined upward) surface roll forward when the brake pedal is released?
When a vehicle braked, it uses friction to counteract and dissipate the momentum [1]. However, when the brake pedal is released, the car continues to roll forward because the momentum of the wheels needs to be counteracted by the ground forces [2].
Automatic transmission cars creep forward when the brake is released because the engine is still spinning, even when the car is stopped [2][3]. The torque converter, which is part of the automatic transmission, allows the engine to spin with the wheels stopped, creating the creeping effect [2][3].