The formula for calculating downstream velocity is Vd = Vr + Vw, where Vd is the downstream velocity, Vr is the velocity of the boat relative to the water, and Vw is the velocity of the water.
The distance traveled downstream can be measured using a GPS device or by calculating the distance using a map.
The downstream velocity of a motorboat can be affected by the speed and direction of the water current, the size and weight of the boat, and the power of the boat's engine.
The downstream velocity can change over time depending on the changes in the water current, the speed of the boat, and any changes in the boat's engine power.
Some safety precautions to consider when traveling downstream in a motorboat include wearing life jackets, being aware of any hazards in the water, and maintaining a safe speed to avoid accidents or collisions.