The model illustrates the concept of relative motion using a boat crossing a river as an example. Watch the change in the trajectory of the boat as it crosses the river, while modifying the absolute value and the direction of the boat's velocity, the speed of the river flow, and the boat?s point of departure. Note that the total velocity of the boat v in respect to the shore is a vector sum of the boat's velocity v' in respect to water, and the vector of the river flow velocity v_{0}.