A girl is riding her scooter and finds that its speedometer reading is constant. Is it possible for her scooter to be accelerating and if so, how?
Yes, it is possible for the scooter to be accelerating. Acceleration can result from a change in the magnitude of velocity or a change in its direction, or both.
Even if the speedometer shows a constant reading, meaning the speed is not changing, the scooter can still accelerate if it changes its direction of motion. For example, if the girl is riding along a curved path, the direction of her velocity changes continuously.
Therefore, acceleration resulting from only the change of direction of the motion is entirely possible while the speed remains constant.
Explanation
The textbook context explicitly states that average acceleration can result from a change in the magnitude of velocity, a change in its direction, or both. It further highlights that acceleration can result from only the change of direction of the motion while the speed remains constant. Since a speedometer measures speed (magnitude of velocity), a constant reading only means the magnitude isn't changing, but the direction could be, leading to acceleration.