Acceleration is by definition the change in velocity per unit time.
If the velocity of the girl is uniform at 1.5 m/s, then there is no acceleration.
Remember that velocity is a vector quantity and a vector can change in 3 ways
Magnitude only Direction only Both magnitude and direction. Now the magnitude of velocity (speed) can stay constant while the direction is changing. This is the case in circular motion.
In the question above, it is mentioned that the girl is moving along a straight road. Therefore no change in direction of velocity.
Final Answer: No acceleration because of no change in velocity.
