Irodov Problem 1.2

Mean velocity is total distance by total time. Let the total distance traveled be d. The time taken to travel half the distance (d/2) at speed vo is d/(2vo). Now another d/2 distance remains to be traveled. Now let the time taken to travel this remaining distance be t. Then (t/2)v1 + (t/2)v2 = d/2. This means that t = d/(v1 + v2).

The total time traveled thus is, d/(2vo) + d/(v1 + v2). The total distance is d. Thus, the mean velocity is,