Final answer:
The position of a boat on a calm sea exemplifies relative velocity, where the boat's motion is observed relative to the sea's stillness. The boat's velocity is the result of its own motion as there are no additional external factors like currents affecting it.
Step-by-step explanation:
The position of a boat moving on a calm sea is an example of relative velocity. This concept is observed when the motion of an object is considered in relation to another object, which can be both calm or in motion. For a boat on a calm sea, if it moves at a constant velocity and then decelerates, what we're observing is relative to the sea itself, which is not contributing any additional velocity to the boat. It then continues to slow down, first at a steady rate, then at a decreasing rate of deceleration, until it comes to a stop.
In contrast, relative velocity can manifest very differently when external factors like currents and winds come into play. For example, a boat trying to cross a rapidly flowing river will move diagonally due to the river carrying it downstream, even though it's trying to head directly across. This is because the boat's resultant velocity is the vector sum of its own propulsion and the river's current—another instance of the classical addition of velocities.