If the speed in the first half of the journey is 5m / s, and the speed in the second half of the journey is 3m / s, the average speed of the whole journey can be calculated In a hurry

If it is a linear motion in a single direction, the distance of the whole course can be set as s, and the average speed of the whole course can be set as v,
V flat = s / T total
= s / (before t + after t)
= s / [(before 0.5s / V) + (after 0.5s / V)]
= V front * V rear / [0.5 * (V front + V rear)]
＝5*3 / [ 0.5*(5＋3) ]
＝3.75 m/s

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