Final answer:
When walking the dog and turning a corner, the velocity changes due to a change in direction.
Step-by-step explanation:
When Jen is walking her dog at a constant rate and they turn a corner, their velocity changes because velocity is a vector quantity that includes both magnitude (or speed) and direction. If they were walking in a straight line with a constant speed, their velocity would remain the same. However, when they turn a corner, their direction changes, which means their velocity has changed.