The speed of a boat in still water is v. The boat is to make a round trip in a river whose current travels at speed u. Part A Derive a formula for the time needed to make a round trip of total distance D if the boat makes the round trip by moving upstream and back downstream. Express your answer in terms of the variables D, v, and u.

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Ithink the answer would be a