Poetry uses forms and conventions to suggest differential interpretation to words, or to evoke emotive responses. Devices such as assonance, alliteration, onomatopoeia and rhythm are sometimes used to achieve musical or incantatory effects.
The average speed of an object tells you the (average) rate at which it covers distance. If a car's average speed is 65 miles per hour, this means that the car's position will change (on the average) by 65 miles each hour.
What about the average speed according to definition 1? In this case, the distance traveled is 1000 meter so that the average speed would be (1000 m)/(50 s) = 20 m/s. This is what the speedometer would read. According to definition number 2, the average speed is the magnitude of the average velocity. Since the average velocity is zero (vector) m/s, the magnitude of this is also zero meters per second. If you want the instantaneous speed according to the definition 2, that would also be 20 m/s.