Maintaining speed on an incline is still acceleration. Gravity is just also accelerating you in the opposite direction. The problem here isn't with the parent's

Maintaining speed on an incline is still acceleration. Gravity is just also accelerating you in the opposite direction. The problem here isn't with the parent's mental model of how pressing the pedal is supposed to work, it's with your mental model of what acceleration means. It doesn't mean the number on the speedometer goes up.