Final answer:
In Physics, the change in the velocity of the bus, as it speeds up from 15 m/s to 20 m/s south, is a 5 m/s increase in speed toward the south.
Step-by-step explanation:
When discussing the changes in velocity of a bus, we're dealing with concepts in Physics, specifically kinematics. Velocity is a vector quantity, meaning it has both magnitude and direction. The change in velocity is known as acceleration (when the velocity increases) or deceleration (when it decreases).
In this scenario, the bus speeds up from 15 m/s to 20 m/s, all in the south direction. The change in velocity is then simply calculated by subtracting the initial velocity (15 m/s) from the final velocity (20 m/s).
The change in velocity is therefore: 5 m/s south. This represents an acceleration since the bus's speed increased while moving south.