For a straight-line motion at constant speed.
Work Step by Step
Example: I am driving my car in a straight-line. My speed is 30 m/s and constant. Starting at the origin: For t = 1 s, x = 30m. For t = 2 s, x = 60 m. And so on. This way, my average and instantaneous velocity are the same. If I am not driving my car in a straight-line the direction is changing. But, velocity is a vector and, even if the speed of my car is constant, my velocity is changing.